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The Library of Congress 



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for Audio Visual Conservation 

Motion Picture and Television Reading Room 

Recorded Sound Reference Center 




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That is what the managers of almost 6000 theaters have learned 
— more than one-third of the theaters in the country. 

Simplified High Intensity projection costs so little 
more than low intensity that one more patron per 
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It puts your theater in line for successful competition 
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JANUARY 193 9 

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Edited by James J. Finn 

Volume 14 


Number 1 

Index and Monthly Chat .... 


Receiver Sale Premature — 

Zenith Prexy 


Matching Various Units of 

E. F. McDonald, Jr. 

Theatre Public Address Sys- 


Academy Report on Television 


Aaron Nadell 

Compensation Laws Sizzle Craft 


Television and the Future of the 
Motion Picture Theatre .... 


Merle Chamberlin 

James J. Finn 

Letters to the Editor 


Technical Data on New RCA 


Fourth Subscription Contest 
Diagram; Few Winners on a 

New RCA Units Graphically 
Shown . 


Simple Circuit 


News Notes 

The Road Ahead for Television 


Technical Hints 

I. J. Kaar 

Miscellaneous Items 

Published Monthly by 


Circulation Manager, Ruth Entracht 

Subscription Representatives 

Australia: McGills, 183 Elizabeth St., Melbourne 
New Zealand: Te Aro Book Depot, Ltd., 64 Courtenay Place Wellington 
England and Dominions : Wm. Dawson & Sons, Ltd., Pilgrim St., London, E. C. 4. 

Yearly Subscription: United 
States and possessions, $2 (two 
years, $3) ; Canada and foreign 
countries, $2.50. Single copies, 
25 cents. Changes of address 
should be submitted two weeks 
in advance of publication date to 
insure receipt of current issue. 
Entered as second-class matter 

February 8, 1932, at the Post 
Office at New York, N. Y. under 
the act of March 3, 1879. 
Contents copyrighted 1939 by 
James J. Finn Publishing Corp. 
International Projectionist 
is not responsible for personal 
opinions appearing in signed 
articles in its columns. 

Monthly Chat 

ROAMING through the far reaches 
of upper N. Y. State, Canada and 
the Middle West during the past month 
we visited with and addressed 16 I. A. 
Local Unions. The chief topic? Tele- 
vision, of course. Too much about the 
technical aspects of this art neither we 
nor our hosts knew or know, but we 
were surprised at the pessimism evi- 
denced anent the effect of television 
upon the future of the motion picture 

Nobody with whom we spoke doubted 
that theatres would be slaughtered by 
the advent of television; the question 
unvaryingly posed was "How soon?" 
Fortunately or otherwise, depending 
upon one's viewpoint, we had prepared 
a little talk on this very topic; and 
strangely enough, after we had given 
this speil the boys felt a little better. 
This parcel of gab, together with other 
assorted data anent television, is pub- 
lished elsewhere herein. See how you 
feel after digesting it — not forgetting, 
of course, that the opinions of I. P.'s 
editor are those of one who is also 
trying to find his way out of the dark- 
ness into the light. 

We have always held that 99% of 
I. P. readers cared little about studio 
projection procedure. Publication of 
Merle Chamberlin's article last month 
gave us a severe shock and forced us 
to admit we were wrong — to just about 
the extent of the aforementioned per- 
centage. This being so, we have planned 
another little foray into the studios, the 
results of which will be available 
shortly. Don't run, Merle. 

INCIDENTALLY, the craft is running 
a fever induced by that decision of 
the Oklahoma State Supreme Court 
(I. P. last month) upsetting a com- 
pensation award to a projectionist 
badly burned in a theatre fire and 
classifying projection work as a "non- 
hazardous" occupation. Mr. Chamber- 
lin suggests that I. P. "take up the 
cudgels" in behalf of the craft in this 
situation. Our opinion that this is 
properly a job for the state or district 
legislative bodies doesn't mean that we 
shan't see what can be done about this. 
Where, oh where are those projection- 
ist technical organizations (A.P.S. and 
P.A.C.) now? 

• • • 

On a recent Sunday night within a 
four-hour period there were only 24 
ranking Hollywood film players on the 
three major radio networks. Without 
picture contracts these "players" (and 
are some of them terrible ! ) couldn't 
even get into a broadcasting studio. 
Not forgetting the studio audiences at 
these gay little parties — while theatre 
cashier's hands are freezing through 

JANUARY 19 39 


Manufactures a Complete Line of Projection Lamps 

A background of 28 years experience producing light projection equip- 
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every theatre requirement 


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lamp of theatres of medium size throughout the world . . . 
Projection is at its best with the Brenkert Enarc . . . Unit 
construction makes all parts easily accessible . . . Continu- 
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The leading projection lamp for large metropolitan theatres 
throughout the world . . . All major motion picture studios 
in Hollywood use the Brenkert Model A Lamp as standard 
equipment for rear projection in the taking of motion pic- 
tures . . . Literature upon request. 


An entirely new lamp that increases screen illumination 
with regular standard low-intensity carbons and equipment 
. . . An enlarged lamp house with new ventilating system 
enabling you to maintain lower lamp house temperatures 
. . . Folding doors that take up less operating space in your 
projection room . . . Fully automatic with advanced elec- 
trical, optical, and mechanical features . . . Automatic 
carbon alignment . . . Literature upon request. 






FEB -2 1939 / 

©C1B 405212 ^C ^ 





Matching Various Units of Theatre 
Public Address Equipments 

MATCHING equipment com- 
ponents for theatre p. a. work pre- 
sents theoretically the same prob- 
lems encountered in sound picture 
systems, but in practice the projection- 
ist is often confronted with special diffi- 
culties. Sound picture equipments are 
usually delivered to the theatre as en- 
gineered units, the components of which 
have been properly matched in factory 
design. They serve the single purpose 
of film reproduction. 

Public address apparatus, to the con- 
trary, usually is required to perform a 
variety of services, from reinforcements 
to ballyhoo. Except in the largest thea- 
tres, it is likely to be not an engineered 
unit but a patchwork; managers tend 
to call for additional microphones, 
speakers, etc., as needs for enlarged 
facilities arise, and the man in charge 
is responsible for matching 'the new 
parts to the old ones. If the p. a. sys- 
tem has been built up around the sound 
picture amplifier, as it often is, the re- 
inforcement parts must match not only 
each other but the synchronous equip- 
ment as well. 


Furthermore, p.a. work involves a spe- 
cial requirement in the way of securing 
satisfactory match, which may be refer- 
red to conveniently as coordination of 
frequency response. Suppose that a 
loud speaker, for example, is 3 db more 
efficient at 1,000 cycles than at any other 
level. Such a condition is common, and 
when not carried to extremes, is un- 
important practically. 

• Frequency Coordination 

Now, if the amplifier also has a 3 db 
peak at 1,000, the system as a whole 
presents a 6 db peak at that frequency. 
If several different components all peak 
at the same tone, it is obvious that the 
system as a whole will produce distorted 
sound. Consequently, interacting com- 
ponents that do not have a truly flat 
response (few have) should at least be 
so coordinated that they will not rein- 
force each other's defects. With a 
speaker of the kind indicated, the am- 
plifier should peak, if at all, at some 

frequency other than 1,000 and other 
than a harmonic of 1,000. 

Now, in talking picture systems, im- 
perfect frequency coordination does no 
harm other than to impair the sound 
quality. With microphone equipment 
the results may be far more serious, 
for if the system is peaked to the ex- 
tent of introducing acoustic feedback, 
it will not work at all. Nothing will 
be heard but a squeal or howl at the 
pitch of the frequency in question. 

This point was touched upon in I. P. 
recently 1 , but its relation to proper 
matching of apparatus was not stressed 
at that time. Briefly, loud speaker sound 
re-entering the microphone where it 
originated is again amplified, again 
leaves the loud speaker and returns to 
the microphone to undergo further am- 
plification, and so on. The unavoidable 
requirement of microphone operation is 
this: the loss in volume between loud 
speaker and microphone must be greater 
than the gain of amplification between 
microphone and loud speaker. 

When the desired condition exits, it 

iDec, 1938, p. 3. 


is obvious that each time the sound goes 
round the circle it gets back to the 
microphone weaker than it was the last 
time, so it soon dies out. When, how- 
ever, the amplification is greater than 
the loss in air between loud speaker 
and mike, it is plain that every time 
the sound gets back to the microphone 
it will be stronger than previously, and 
instead of dying out it will increase in 
strength up to the power limits of the 

It is plain, further, that the tone or 
frequency at which the system is most 
efficient will be the one most quickly 
built up to the limit of system power. 
Hence that one frequency, under those 
circumstances, will be the only one 

To avoid this condition it is neces- 
sary to either cut down amplification 
or increase the air loss between loud 
speakers and microphones, or both. 
Both means are employed. But if the 
system is exceptionally efficient (highly 
peaked) at some one frequency, feed- 
back may occur at that frequency long 
before the volume control has been 
brought up high enough to make the 
sound as a whole usable. Under those 
circumstances satisfactory operation is 
impossible. Equipment components of 
a flatter characteristic response must be 
substituted. That means more expen- 
sive components. 

Coordinating components which are 
somewhat peaked, so that they don't 
all peak at the same tone, is one way 
of reaching an acceptable compromise. 
When the system as a whole is suffi- 
ciently flat, proper speaker placement 
and baffling, proper choice and place- 
ment of microphones, or use of direc- 
tional microphones, or all three, will 
allow volume to be brought up to the 
point of satisfactory operation with- 
out so strongly accentuating any one 
tone as to allow feedback to set in. 

As a practical problem in p. a. work, 
this matter is almost entirely one of 
choosing suitable microphones and 
speakers. It is comparatively easy and 
inexpensive to build an amplifier of a 
satisfactorily flat response, and ampli- 
fiers built nowadays have few if any 
significant peaks in their action. Truly 
accurate curves of microphone and 
speakers can be obtained from all the 
better makers; but if there is any ques- 
tion of the curve having been drawn 
with sufficient detail, the manufacturer 
may be queried as to the frequencies 
at which any significant peaks appear. 
All the more reputable makers will an- 
swer accurately. 

Aside from frequency coordination, 
p. a. apparatus presents distinctly im- 
portant problems of impedance match 
and power match. It is customary to 
figure these problems by beginning with 

loud speakers — which represent the per- 
formance requirements — and working 
backward. But in theatre installations 
it is often desired to make use of the 
sound picture amplifier and build p. a. 
equipment around that. In such cases 
one can only begin with the amplifier 
and work outward in both directions. 
Speaker arrangements should be investi- 
gated first, however, because if the am- 
plifier cannot possibly meet the speaker 
requirements (that is, give the neces- 
sary performance) it is useless to con- 
sider it further; another amplifier will 
have to be obtained for p.a. purposes. 

• Speaker Power Requisites 

It is important to note at once that 
the ability of an amplifier to provide 
sufficient sound for talkie purposes does 
not mean that the same amplifier can 
provide adequate p.a. volume. That 
would follow only if the p.a. speakers 
were fully as efficient as the sound pic- 
ture speakers. But it so happens that 
the better sound picture systems use 
speaker units that range up to thirty 
percent efficiency or better, whereas the 
more common radio or p.a. speakers 
can often convert into sound energy only 
five or ten percent of the power they 
receive as electrical energy, wasting the 
rest as heat. 

It is clear that the same amplifier 
may be unable to fill a theatre with 
sound when called on to work through 
speakers of materially lower efficiency. 
The first problem with reference to using 
a talkie amplifier for p.a. work is, there- 
fore, consideration of speaker efficiency 
differences in relation to the amplifier's 
reserve power capacity. This means in 
practice than an amplifier customarily 
operated at or near peak volume for 
talking picture work will be of dubious 
utility for p.a. sound. 

But a gain of 3 db is equivalent to 
doubling volume; if the amplifier gain 

Getting the 'Bird' 

Credit Charley Dentlebeck, super- 
visor of projection for Famous 
Players Canadian. Corp., for passing 
along this all-time, all-champ pro- 
jection room report: 

"Four interruptions within an 
hour due to a bird getting into the 
ventilating system and working its 
way through the lamphouse into the 
back shutter of No. 1 projector, 
causing stoppage. Film was trans- 
ferred to No. 2 projector; five- 
minute delay. Three other delays of 
one minute each for re-threading 
No. 2 projector while trouble was 
being cleared on No. 1. Following 
gears replaced: G-112-G, P-220729, 
and G-134-G." 

We know they grow them big in 
Canada (the birds, we mean) but 
stripping gears in this manner 
would require at least an eagle. 
Incidentally, title of picture was 
"Goldwyn Follies". 

is raised 6 db, its output is increased 
four times; a 9 db increase (three steps 
on some types of volume control) is a 
power gain of 2 x 2 x 2, or 8 times. 
Such a gain will easily be enough to 
compensate for any reasonable differ- 
ences in speaker efficiency. It may not 
be enough, however, to compensate for 
the use of additional speakers, as some- 
times required for the lobby or for bally- 
hoo outside the box office. 

These considerations apply with equal 
force whenever additional speakers are 
for any reason to be wired to existing 
p.a. equipment. They also involve a 
special difficulty in that comparatively 
few manufacturers either do or can give 
accurate information anent the efficiency 
of their speaker units. Consequently 
if the picture sound system uses loud 
speakers especially designed for that 
form of service, it will generally be ad- 
visable to figure on at least a 9 db in- 
crease in amplifier output for p.a. 
speaker units of fairly good quality. If 
the picture system makes exclusive use 
of speakers of the p.a. type (as some 
do) allowances are clearly unnecessary. 
This latter condition will be the ex- 
ception rather than the rule. 

• Speaker Power Distribution 

Some sound picture systems, espe- 
cially in small houses, use only a single 
loud speaker (centrally located behind 
the screen), but two speakers at least 
represent the minimum for ordinary re- 
inforcement work. To conceal the 
source of artificial sound from the 
audience it is sometimes necessary to 
use many more than two. The total 
power output may be divided among the 
speakers equally or unequally according 
to the requirements imposed by the in- 
dividual auditorium in the matter of 
good acoustic results, and good illusion. 

A possible source of confusion should 
be avoided at this point by noting that 
distribution of volume among speakers 
to obtain good acoustic results and good 
illusion has nothing in common with 
the distribution of power between high- 
frequency and low-frequency units in 
modern sound picture systems. The 
p.a. system that uses separate h.-f. and 
l.-f. speakers is so rare as to be almost 
non-existent in modern theatre work. 
The vast majority use a single set of 
speakers for all frequencies, conse- 
quently the problem of distributing vol- 
ume among them has nothing to do with 
frequency filter networks; it is a 
relatively simple matter of respective 

If all speaker units are connected 
across the same set of amplifier output 
terminals, and if all are of the same 
impedance, then necessarily all will re- 
ceive the same proportion of the total 

If the speaker line impedances are 




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not all the same, then the current will 
divide among them inversely to imped- 
ance, the speaker line having the high- 
est impedance receiving the least power, 
and vice versa. 

A simple way of obtaining unequal 
line impedances for the purpose of caus- 
ing power to divide unequally is to equip 
certain speaker lines with individual 
volume controls. In the interest of 
economy, controls are not associated 
with those speakers that are to work 
loudest. Sound is set to suit these at 
the amplifier volume control, and the 
individual controls associated with the 
other units (or groups of units) are 
then adjusted accordingly. 

Simple potentiometers can be used for 
such controls, at a cost probably of less 
than one dollar each (depending upon 
the power requirements), but this is not 
the best practice. Pads of some type, 
ladder pads for example, can be ad- 
justed to vary the speaker volume with- 
out changing the pre-determined line 
impedance. (A related but less effec- 
tive form of volume control, the T-pad 
circuit, is traced in I. P. for July, 1935, 
pp. 10-11.) 

The use of pads for individual speaker 
controls is open to the practical objec- 
tion that they are somewhat expensive, 
particularly when the power involved 
exceeds two or three watts. Further, 
there is no real need for pads where 
individual speaker volume is not to be 
varied from time to time but will be 
permanently fixed with reference to the 
volume from all other speakers. 

The simplest and most effective of all 
methods of securing any desired degree 
of unequal distribution of volume is to 
choose the individual speaker imped- 
ances suitably. This method can best 
be described after normal methods of 
matching impedances have been con- 

• Speaker Impedance Match 

Accepting as accurate manufacturers' 
ratings of the impedances of parts and 
circuits, the simple arithmetic for im- 
pedance calculations in the theatre is 
exactly the same as that for figuring 
d.c. resistance (discussed in quite some 
detail in I. P. for Nov., 1938, pp. 7-9). 
In ordinary p. a. work as encountered 
in the theatre amplifier output trans- 
former secondaries, speaker input trans- 
former primaries and speaker voice 
coils are treated exactly as if those 
parts were straight resistances working 
on d.c. The only difference is that the 
ohmmeter cannot be used to check the 
manufacturers' ratings, or to substitute 
for them. 

Consequently, if an amplifier is built 
with a 500-ohm output, and four 
speakers are to be used, each having 
2,000 ohm transformer primaries, the 
four need only be connected in parallel 

Compensation Laws Sizzle Craft 



THE action of the Oklahoma State Supreme Court in setting aside a com- 
pensation award to one Albert G. Johnson for burns suffered during a 
projection room fire (I. P. for Dec, p. 24) occasioned considerable com- 
ment among West Coast projectionists, and, I am sure, among members of 
the craft throughout the country. Classification of projection work as "non- 
hazardous employment" because it does not constitute a "workshop" under 
Oklahoma law is sharply inconsistent with the generally adopted view else- 
where anent the many occupational hazards incident to motion picture projec- 
tion work. 

Being keenly interested in this matter, I endeavored to ascertain through 
the M-G-M Studio compensation representative the significance of this Okla- 
homa decision. The appended reply from the insurance brokers, while con- 
cerned primarily with the California compensation law, contains sufficient 
information of general interest to warrant attention by projectionists through- 
out the country: The letter, in part, follows: 

"You have asked us to give an opinion . . . whether in the light of 
this decision a projectionist working in California would be covered under 
the compensation laws. 

"The point involved in the Oklahoma case . . . would not arise under 
the California law. The Oklahoma Act applies to 'manual or mechanical 
labor of a hazardous nature . . .' Apparently, from the recitation of facts 
when this particular case was submitted to the Industrial Commission of 
Oklahoma, they decided that the occupation was 'of a hazardous nature' 
within the meaning of the Act. The case was appealed, and the State Supreme 
Court set aside the award of the lower court and held that the State law did 
not classify occupation in the theatre industry as hazardous employment 
within the meaning of the Act. 
• State Compensation Laws Vary Widely 

"The California Act differs materially in that it does not restrict appli- 
cation of its laws to certain forms of employment. Under the heading of 
'Employment Covered' the California Act covers 'all public and private em- 
ployments.' There are certain minor exceptions that have no bearing on 
this case. 

"A considerable number of state compensation laws contain provisions 
similar in form to the Oklahoma Act in that they are intended to apply only 
to so-called 'hazardous employment.' The status of projectionists has been 
doubtful under many of the acts and is generally considered borderline. In 
some states, notably Washington and Oregon, where the acts apply only to 
hazardous employments, it has been held specifically that projectionists come 
within this class. 

"We handle the insurance for several theatre chains extending into these 
states, and have found it necessary to purchase special State Fund Insurance 
on projectionists employed in these theatres. The Compensation Act does 
not apply to any other theatre employees, who are treated separately from 
the insurance standpoint." 

The foregoing letter says it all — or at least enough to warrant the state- 
ment that I. P. would be doing a wonderful service to the craft if it would 
take up the cudgel and clarify the status of projectionists under the com- 
pensation laws of the questionable states, of which I understand there are 

to provide a perfect match. Similarly, 
four 125-ohm speakers (or their trans- 
formers) could be wired in series to 
match. In either case, volume would 
be divided equally among all speakers. 
Where unequal volume is wanted, as- 
sume for example that two of the 
speakers are to be given only one 
quarter as much power as their partners : 
a simple solution might be to connect 
the 500-ohm inputs of the two low-vol- 
ume speakers in series, making a 1,000- 
ohm circuit. Connect the 500-ohm in- 
puts of the two high-volume speakers 

in parallel to create a 250-ohm circuit. 
Division of power between these two 
circuits will then be in the ratio of 4 to 
1. and both can be connected to a 200- 
ohm amplifier output for a perfect 
match; or if the amplifier is not so 
equipped, the 250-ohm output terminals, 
which are more common, will give a 
mismatch of only 20 percent, which is 

In more complicated cases very in- 
teresting gradations of power can be 
effected, even among a relatively large 
number of speakers, by following the 



same general method. Loud speakers 
of the public-address type are commonly 
obtainable equipped with input trans- 
formers having a large number of taps 
to their primary windings, giving a very 
free choice of available input imped- 
ances; and p.a. amplifiers, unlike sound 
picture amplifiers, are usually built with 
output transformers offering an option 
among as many as perhaps twenty dif- 
ferent output impedances. 

Further choice still can be had by 
eliminating the speaker input trans- 
formers and wiring to the voice coils 
direct. With these facilities available, 
a little patience and trial-and-error (on 
paper, not in actual wiring) will make 
possible almost any desired loud speaker 
arrangement, to suit all theatre prob- 
lems. Very complicated requirements 
may even call for several hours with 
pencil and paper involving nothing more 
difficult than the arithmetic of fractions. 

The real difficulty of the work lies in 
determining in advance just what per- 
centage of the total volume output each 
individual speaker should have. That 
may call for some trial-and-error work 
in actual wiring, changing speaker trans- 
former tap connections until a number 
of actual trials have given fair insight 
into the real requirements. All such 
tests should also be calculated in ad- 
vance to make certain what is the exact 
distribution in each case. 

This method is particularly suitable 
where additional speakers are to be 
added, either in an auditorium, in a 
lobby or outdoors. Granting only that 
the amplifier has enough reserve power 
to accommodate the addition, proper im- 
pedance match can readily be preserved 
when wiring-in new speakers, and cor- 
rect allocation ol volume to the new- 
comers arranged at the same time. 

• Multiple-Service Units 

In some theatres some or all of the 
p.a. apparatus is used for more than 
one function. Certain components may 
even be portable or semi-portable in na- 
ture. The simplest example is when a 
microphone, normally used on the stage, 
is unplugged for temporary use on a 
sound truck. However, the amplifier 
itself may be transferred to a truck on 
occasions when it is not needed inside 
the theatre. A variation is to take a 
sound truck amplifier into the theatre, 
along with a storage battery to provide 
power for its operation and a charger 
to keep the battery in condition. Some 
special p.a. amplifiers can be made to 
work either from a 6-volt storage battery 
or from a 110-volt a.c. line, merely by 
plugging in different power connections. 
They are not particularly expensive. 

One item of equipment, however, is 
seldom transferred outside the audi- 
torium. Speakers and baffles best suited 
to indoor work are not always adaptable 

to outside operation. In addition, really 
satisfactory speaker placement and ad- 
justment lor best auditorium results is 
usually too difficult to obtain to justify 
upsetting it for any trivial reason. Buy- 
ing a separate set of speakers for out- 
side work is likely to prove more eco- 
nomical in the end. For all these rea- 
sons the auditorium speaker setup is 
seldom disturbed. 

However, some one speaker, so located 
as not to need too critical pointing, may 
occasionally be removed to serve tem- 
porarily . outside the box office, or to 
lend sound effects to some ballyhoo cut- 
out or attraction sheet. A number of 
interesting tricks have been used for 
front-of-the-house appeal, including the 
old one of the cutout wizard, wired with 
a microphone and speaker, who answers 
the questions of passersby. 

A variation in the way of flexibility 
which does not involve the physical re- 
moval of any apparatus, hence is prefer- 
able, is based on the method of wiring 
in supplementary speakers — at the 
marquee, in the lobby, in the lounges 
or elsewhere — but playing them only at 
selected times. 

Maintaining impedance match regard- 
less of the switching of such speakers is 
simply a matter of using a d.p.d.t. switch 
and a dummy load resistor. The dummy 
resistance in ohms will equal the speaker 
input impedance in ohms, and both will 
have the same power rating. The total 
line impedance is then calculated ex- 
actly as if the speaker in question were 
always in use, which in effect it is — 
when it is not playing the dummy load 
effectively takes its place for all elec- 

iiiral purposes. Similarly, if an audi- 
torium speaker is temporarily removed, 
whether for use on another circuit or 
only for repairs, a suitable resistor 
should be connected in its place. 

• Speaker Field Matching 

Matching speaker fields is a matter 
of maintaining correct resistance and 
wattage values. Until recently it was a 
subject just as important and difficult 
as maintaining impedance match, and 
handled in much the same way. The 
advent of effective, high-power perm- 
anent magnet speakers has greatly 
minimized this problem. 

Whenever additional speakers are to 
be installed, the permanent magnet kind 
can be used, eliminating all excitation 
problems and saving enough in wiring 
costs to more than make up the small 
difference in price. However, many p.a. 
amplifiers still are built with speaker 
field exciting circuits incorporated in 
their power arrangements. Where these 
exist, the power they provide must be 
dissipated in some ay. A bleeder re- 
sistor may be connected across the field 
power output terminals, or all or some 
of the speakers used may be of the 
electro-dynamic type to take advantage 
of the power available. Generally, how- 
ever, permanent magnet units are prefer- 
able as being slightly less likely to break 
down, less complicated to investigate 
in emergencies, less expensive to wire 
and incapable of producing hum on their 
own account. 

Matching of microphones and other 
input sources will be discussed in a 
subsequent issue. 

Letters to the Editor 

To the Editor of I. P. 

As you know, I read every word of 
your excellent publication (which is 
just too bad for you sometimes, this 
being one of them) and almost always 
I find myself in agreement with you. 
In your Monthly Chat for the Dec. 
issue, however, you state: "The year 
1938 can be marked down as one of 
the dullest ever from the standpoint of 
progress in projection equipment and 

Now, I believe it to be time that you 
read your own publication as diligently 
as do your readers, particularly myself. 
In your issues for April and May, 1938, 
you commented at length about the 
wonderful strides forward represented 
by the new Simplex E-7 projector and 
the Simplex 4-Star Sound System. "Will 
you love me in December as you did 
in May?" 

If your statement in this instance be 
correct, then it cost this company about 
$300,000 to prove you right and our- 
selves wrong. However, reports from the 
several hundred theatres which have in- 
stalled the aforementioned equipment (I 

shan't mention the name Simplex) in- 
dicate that we did a pretty good job 
on this equipment. 

Well? ... I don't like the taste of 
crow myself. 

Herbert Griffin 
International Projector Corporation 

[ED.'S NOTE: A swell job by In- 
ternational Projector being one of those 
things that is taken for granted by the 
industry throughout the world, the 
super-excellence of the "aforemen- 
tioned" equipment (I shan't mention 
the name Simplex) needed no special 
reference. The foregoing is probably 
the first wholly truthful alibi on rec- 

To the Editor of I. P. 

In my article anent Studio Projec- 
tion in I. P. for Dec: on page 16, 
second column, second paragraph ap- 
pears the statement, "... or without 
inducing poor definition as a result of 
an abnormally small stop in the lens." 
This statement was originally written 
as, "... or without giving our people 
(the studio) false definition, which an 

JA1VUARY 1939 


abnormally small stop in the lens would 

The substitution of the word "poor" 
for the word "false" might be confus- 
ing to some readers. I elected to use 
the word "false" because an abnormally 
small stop will give abnormally sharp 
definition, which is impossible to obtain 
in a majority of theatres. Naturally, 

my policy is to give our executives pro- 
jection approximating that obtainable in 
theatres, thus I avoid the false defini- 
tion which would result from a small 
stop, which I could very easily use with 
the great quantity of light available. 

Merle Chamberlin 

Supervisor of Projection 

Metro-Goldwyn-Mayer Studios 

Fourth Subscription Contest Diagram; 
Few Winners on a Simple Circuit 


THE switch from the better known 
types of sound picture circuits to 
those intended for other purposes ap- 
parently has toughened up the Diagram 
Contest considerably. Yet there is no 
reason why one who is assumed to 
know his circuits should be either stuck 
by or object to the switch in type of 

This month's Contest entry (Fig. 1) 
is of a type that affords an equal 
chance for all, the possibility of any- 
body being overly familiar with it either 
through use or by consulting a refer- 
ence work being remote. Which is ex- 
actly as it should be. Most of the cir- 
cuit has been redrawn, thus rendering 
futile any detective work through faulty 
draftsmanship. The several errors con- 
tained therein refer not at all to circuit 
constants, being related exclusively to 
connections. What's difficult about that? 

As is customary, only subscribers 
to I. P. are eligible to compete in this 
Contest. All answers must reach I. P. 
not later than Feb. 20. The award 
will be the same— one year's free sub- 
scription to I. P. for every successful 
contestant. It is not necessary to en- 
close a copy of the Contest diagram, 
although this is elective on the part of 

Last month the boys again did not 
do so well. Incidentally, the circuit 
was that of the W.E. 108-A voice am- 
plifier used for broadcast work (Fig. 


2 ) . There were only eight winners out 
of more than 100 contestants. Here 
is the listing of the errors therein: 

1. Jumper added between input ter- 
minal 21 and input terminal 22. 

2. Jumper added between output 
terminal 15 and filament of E-3. 

3. Connection (dot) removed from 
first crossing below left-hand side of 

4. Connection (dot) removed from 
crossing, top terminal of R-7. 

5. Connection (dot) inserted at 

crossing between terminal 7 of T-3 
secondary and filament of V-4. 

6. Condenser C-7 short-circuited 
across its plates. 

Reversing these changes in the dia- 
gram will give the correct circuit. Some 
contestants seemed puzzled by meter 
M-l, which connects across the output 
line externally to this diagram. Others 
thought M-2 incorrectly wired as an 
ammeter, whereas in fact R-3, R-9 and 
R-15 serve as shunts for it in a stand- 
ard ammeter hookup. Others failed to 
see that R-10 and C-6 constitute a re- 
verse-feedback circuit. One contestant 
was unfamiliar with the internal sup- 
pressor grid-cathode connection in V-3. 

The eight contestants who scored on 
last month's entry are as follows: Fran- 
cis L. Hill, St. Petersburg, Fla.; Rus- 
sell A. Schrempp, St. Louis, Mo.; 
George Wilde, Columbia, Jll. ; C. H. 
Perry, Sudbury, Ont., Canada; R. W. 
Rushworth, Baltimore, Md.; E. C. 
Wiley, Galesburg, HI.; M. G. Haskin, 
Detroit, Mich.; Howard Hartzell, Phil- 
lipsburg, N. J. 

• Craft's Poor Showing 

Indicative of something or other (we 
haven't decided yet) is the fact that, 
although many different men try their 
hands at these problems each month, 
the winners each time seem to be re- 
stricted to a certain select group. Now, 
it's difficult to believe that a knowledge 
of circuits is confined to men like 
Wilde of Illinois, Hill of Florida, Perry 
of Canada, Mervine of Penna., Hinshaw 
of Idaho and certain others who are 
consistent winners. Yet we find these 
names in the winning column month 
after month, irrespective of the total 
number of entries. 

To say that "these men know their 
stuff" and let it go at that would be 
something less than" accurate. Yet, 
there it is. Considering the wealth of 
circuit material that has appeared in 
I. P., and the amount of money spent 
by many Locals for instruction, the 
results are hardly complimentary to the 



FIGURE .1. Photograph of picture tube image in England FIGURE 2. Photograph of picture tube image in America 

The Road Ahead for Television 

FOR several years the public has 
been increasingly curious to know 
when television would be intro- 
duced commercially, and a great variety 
of explanations have been advanced by 
uninformed persons as to why it has not 
happened already. Of course, at first 
the reason was lack of technical quality ; 
but in the past few years the quality 
of pictures achieved has certainly been 
good enough to interest an increasingly 
large proportion of the population. 

However, two major questions Still 
had to be answered before the wide- 
spread commercial introduction of tele- 
vision. The first of these was the fix- 
ing of satisfactory television standards 
and the second was the discovery of a 
satisfactory method of paying for the 
programs. The first matter has prac- 
tically been settled; the second has not. 

Television differs from sound broad- 
casting very markedly in the importance 
of standards. In sound broadcasting, 
if the method of modulation (ampli- 
tude, frequency, or phase) is once de- 
termined, any receiver which can be 
tuned to the carrier frequency of a given 
transmitter can receive its program. The 
technical quality of transmitted pro- 
grams can be improved year by year, 
but while this happens, a receiver once 
purchased is always usable, even though 
it may become outmoded as compared 
with current models. 

The situation in television is quite 
different. Due to the use of scanning 
and the necessity of synchronization be- 
tween the receiver and transmitter, if 
transmission standards are changed, re- 
ceivers designed for the old standards 

tj. Soc. Mot. Pict. Eng., XXXII (Jan. 1939). 

By /. J. KARR 


Television standards having been agreed 
upon in the U. S., regularly scheduled 
television programs will be offered soon 
along with commercial receiving sets. 
How good will television be and what 
are the problems — technical, artistic 
and economic — yet to be solved before 
television reaches technical maturity? 
These questions are discussed herein. 

become useless. Because of this fact, 
no responsible manufacturer would sell 
receivers to the public until standards 
were fixed by the industry and spon- 
sored by the Federal Communications 
Commission. Furthermore, American 
manufacturers did not desire to fix 
standards, except at such a high quality 
that widespread and sustained interest 
on the part of the public would be as- 
sured and so that adequate provision 
for continued perfection was possible. 

• Program Cost Problem 

It required considerable technical per- 
fection to justify these high standards, 
but this has now been attained and the 
essential standards have been agreed 
upon. Consequently, it may be said 
with some assurance that the last tech- 
nical obstacle in the path of commer- 
cial television has been removed, at 
least as far as the excellence of the 
picture under proper conditions is con- 

The question of who shall pay for 
television programs has not yet been 
answered. As is well known, the cost 
of sound broadcasting is borne by 

"sponsors," who pay enough for their 
own programs to enable the stations 
and networks to fill-in the unsponsored 
time with sustaining programs of good 
quality and to make a profit in addi- 
tion. However, this situation now re- 
quires the existence of tens of millions 
of receivers in the country with listeners 
who may be induced to buy the adver- 
tised products. 

Such an audience does not exist in 
television and can not be expected for 
several years. Of course, no such audi- 
ence existed in the early days of sound 
broadcasting either, and the receiver 
manufacturers themselves, along with a 
few individual companies who built sta- 
tions for their own advertising pur- 
poses, operated the stations. In those 
days, however, the thought of some- 
thing coming through the air, receiv- 
able at no cost, was an entirely new 
one. People were quite satisfied with 
the new toy as such and program ex- 
cellence was a secondary consideration. 
This, of course, meant that the cost of 
broadcasting (as compared with the 
present) was low. 

Now the public has been educated 
to expect a high degree of excellence 
in program material and it is doubtful 
if mediocre program material in tele- 
vision would be acceptable. This has 
been quite strikingly proved in Eng- 
land. In other words, when television 
is born, it must be born full-fledged as 
far as program material is concerned. 
This, of course, means great expense 
which, undoubtedly, will have to be 
borne by the pioneers. 

In Great Britain commercial tele- 
vision is already a reality and it is of 
interest to consider some of its various 



aspects. American television will be 
quite similar, except for improvements 
based upon the progress of the art since 
the British standards were set. 

Figure 1 is an unretouched photograph 
of an image on the screen of a picture 
tube in England. Fig 2 is a similar 
picture taken in America. 

• U. S. Television Standards 

Let us next briefly consider the tele- 
vision standards which have been 
adapted in this country and the reasons 
for their adoption. The reader is no 
doubt acquainted with the general 
scheme of television used, but a quick 
review of the essentials may be in 
order. At both the camera tube and 
the picture tube, the picture is scanned 
by an electronic spot (beam of elec- 
trons) in a series of adjacent horizontal 
lines. The number of these lines into 
which the picture is divided in the 
scanning process determines the fine- 
ness of vertical detail which is repro- 

After scanning the whole picture, the 
electronic spot then repeats the process 
at a sufficiently rapid rate so that no 
apparent flicker exists. This process 
is essentially the same, as far as the 
effect upon the eye is concerned, as 
that performed by the shutter on a 
motion picture projector. The fre- 
quency of repetition of scanning of the 
whole picture is known as the frame 

In order to conserve ether space, it 
is desirable to keep the frame frequency 
as low as possible. Consequently, an 
artifice is employed in order to increase 
the apparent frequency of repetition. 
This device is known as interlace. In 

frame frequency, is known as the field 
frequency. Now, obviously, if anything 
other than a complete blur is to be 
obtained, it is necessary that the num- 
ber of lines per frame, the order of 
scanning of the lines, and the number 
of frames per second be identical at 
the receiver and transmitter. These 
accordingly, have been standardized in 
America as follows: 

Number of lines per frame = 
N = 441 

Number of frames per second = 
F = 30 

Number of fields per second = 
60 (interlaced) 
To these we may also add the stand- 
ard picture aspect ratio, which is 4:3 — 
in agreement with the value used in 
motion pictures. 

There is a reason for choosing the 
number 441 rather than some other 
number of about the same value. It 
may be shown that a necessary re- 
quirement for a stable relationship be- 
tween the horizontal and vertical scan- 
ning oscillators, is that the number of 
lines per frame be a whole number 
having only small odd factors. Four 
hundred and five lines per frame is the 
figure chosen as standard in Great 
Britain, while in some very fine labora- 
tory pictures shown in Holland, 567 
lines were used. 

There is also a good reason for using 
30 as the frame frequency. It is found 
that unless the frame frequency is a 
multiple or a sub-multiple of the power 
supply frequency, a shadow will move 
across the picture. This moving shadow 
has about the same physiological effect 
as flicker and is very disturbing. How- 


Schematic of a typical 

television receiver 

an "interlaced" picture every other line 
of a picture is scanned, and after the 
whole picture has been scanned in this 
way, the lines in between are scanned. 
This gives the physiological effect of 
scanning the picture twice, as far as 
flicker is concerned, even though all 
details of the picture have been com- 
pletely scanned only once. 

The apparent flicker frequency under 
these conditions, which is twice the 

ever, if the frame frequency is a multi- 
ple or sub-multiple of the power line 
frequency, the pattern of the ripple is 
stationary on the image and it is much 
less objectionable. Therefore, since 60 
cycles is standard in American power 
distribution systems, 30 frames per sec- 
ond has been chosen as standard for 
the frame frequency, since this is the 
smallest sub-multiple of 60 whose 
double is above the maximum flicker 

frequency observable by the human eye. 

Among other matters requiring stand- 
ardization are the synchronizing opera- 
tions at both the transmitter and re- 
ceiver. It is clear that scanning at the 
transmitter and receiver must be ex- 
actly synchronous to within an ex- 
tremely small error. In order to accom- 
plish this, synchronizing signals are 
always transmitted with the picture sig- 
nals. The purpose of these synchron- 
izing signals is to start the scanning 
of both the lines and frames at exactly 
the right time. 

A detailed investigation of synchron- 
izing signals would be out of place 
here, but it may be stated as absolutely 
essential that the type of synchronizing 
signal transmitted should be completely 

The next subject is the frequency 
channel width required in television. 
For effective utilization of the intelli- 
gence available from a standard tele- 
vision picture, there must be complete 
and undistorted transmission of all fre- 
quencies from zero to at least 2,750,000 
cycles. If this signal is used to modu- 
late a radio-frequency carrier, an ex- 
tremely wide frequency channel is ob- 
viously required. 

In order to economize on the use of 
the frequency band thus required, single 
side-band transmission is proposed. The 
system may more properly be termed 
"sesqui-side-band." In this system, the 
elimination of one side-band is achieved 
by the use of band-pass filters which 
have a range of partial transmission 
in the region on either side of the trans- 
mission band. The carrier may be 
placed on one of these edge bands at a 
point where there is approximately 50 
per cent transmission. 

It may be shown that such a system 
has essentially double side-band trans- 
mission for very low frequencies, and 
single side-band transmission for me- 
dium and high frequencies. To return 
now to the question of utilization of 
the frequency channel, it is noted that 
by means of "sesqui-side-band" trans- 
mission the frequency band required by 
the video (picture) signal is reduced 
by almost 50 per cent. 

In transmitting television programs, 
it has been found desirable to transmit 
the picture and sound in the same chan- 
nel. This allows a single oscillator to 
be used for both sight and sound in a 
superheterodyne television receiver, thus 
greatly simplifying tuning. In this sys- 
tem, the sound and sight signals are 
separated by selective circuits in the 
intermediate frequency amplifiers. Fig. 
3 diagrams a typical television receiver, 
showing how it transmits and separates 
the video and audio signals. 

When television is discussed by the 



public, the questions most frequently 
asked are, How good is television? 
How good will it be? and How much 
will it cost? The answers to these 
questions involve such matters as: How 
large will the picture be? How bright 
will it be? How much detail will it 
show? How clear will it be? A dis- 
cussion of these considerations will be 
of interest. 

• The Television Picture 

The standard high-quality television 
system which will possibly be commer- 
cialized shortly will have a 12-inch tube 
with a l x /i by 10-inch picture. Three, 
5, 7, and 9-inch tubes will probably 
also be standard commercial sizes. 
Compared with the size of a motion 
picture or even a home movie, these 
dimensions seem small. However, con- 
sidering the fact that the audience view- 
ing a television picture will ordinarily 
not be more than perhaps four feet 
from the screen (and in the case of 
the small tubes, even one foot from 
the screen) these sizes do have con- 
siderable entertainment value. 

Anyone who has seen good pictures 
on 9-inch or 12-inch tubes will testify 
that when the program is interesting, 
the observer forgets that he is viewing 
television and becomes completely ab- 
sorbed in the action on the screen. 
Nevertheless, it is reasonable to expect 
larger pictures in the best systems of 
the future. Table I shows the charac- 
teristics of some present-day television 

The matter of increasing the size of 
the cathode-ray picture presents some 
serious obstacles. As tubes become 
larger they also become longer and 
their overall size becomes such that it 
is difficult to find suitable cabinets for 
them, Avhich at the same time lend 
themselves to attract styling. For this 
reason, when a 12-inch tube is used, it 
is invariably mounted vertically in a 
cabinet, and the picture is seen as a 
mirror image by the observer. Since 
a mirror causes a loss of light, and 
possible double images and distortion, 
it is an undesirable adjunct at best. 

As a further difficulty, as cathode 
ray tubes are increased in size, they 
require more driving power, which is 
expensive, and higher anode voltages, 
which besides the additional cost, also 
represents a shock hazard. Thus the 
prospect of making cathode-ray tubes 
for home use with screen diameters ex- 
ceeding 12 or possibly 15 inches does 
not seem promising at this time. 

As an alternate method of increasing 
the size of the picture obtainable by 
electronic means, the projection picture 
tube may be considered. In this case 
a very brilliant picture on the screen 
of a 4-inch cathode-ray tube is enlarged 
by an external optical system and is 

projected on a screen to a size of, say, 
3x4 feet. This system requires an 
exceedingly bright tube with a very 
fine spot. The ultimate size of pro- 
jection tube pictures is limited on the 
one hand by the brightness obtain- 
able from a flourescent screen without 
causing its rapid deterioration, and on 
the other hand by the detail which can 
be obtained, which is closely associated 
with the fineness of the spot achievable. 
Projection tube apparatus is probably 
too large, complicated and costly for 
home use, but for public performances 
of television programs it undoubtedly 
has a future. 

Mechanical television systems have 
also been used for obtaining large pic- 
tures, with some degree of success. Of 
these, probably the most noteworthy is 
the system employed by Scophony. This 
system accomplishes modulation of the 
light-wave by utilizing fringe light, pro- 
duced by virtue of passing a primary 
beam through a glass vessel in which 
is held gasoline or benzine, the liquid 
being subjected to vibration from a 
quartz crystal. The resulting modu- 
lated wave is then reflected successively 
by two rotating mirrors at right angles 
for accomplishing line and frame scan- 
ning. In the system as proposed, the 
line mirror rotates at a speed some- 
what faster than 30,000 r.p.m 

• Picture Detail 

Closely associated with the problem 
of picture size is the problem of pic- 

neither can go beyond the effective 
diameter of the electron spot. 

Observers have found that if the 
diameter of a picture element subtends 
less than one minute of arc at the eye, 
a picture contains essentially all the 
detail resolvable by the observer. If 
the observer is considered to be 4 feet 
from the screen, a simple calculation 
will show that there are required 70 
lines per inch, and at 2 feet, 140 lines 
per inch. In present-day high-quality 
pictures on a 12-inch tube, with a 
7% inch x 10-inch picture, and 400 
useful lines,* there are 53 lines to the 
inch. It is not unreasonable, therefore 
to expect the number of lines in tele- 
vision pictures to be a matter for at- 
tention in the years to come. 

Goldsmith states that a high quality 
motion picture screen has 5,000,000 pic- 
ture elements. This would be equiva- 
lent to a 2000-line picture, which would 
give 1 degree resolution on a picture 
3 feet x 4 feet in size, viewed from 
a point 5 feet away. While it is not 
too much to expect such television pic- 
tures sometime in the future, certainly 
a great many problems must be solved 

For example, such a picture would 
require 150,000,000 picture elements per 
second, which, at a conservative esti- 
mate, would need a band width of 80 
megacycles per program for its trans- 
mission. This would undoubtedly re- 
quire the use of quasi-optical carrier 

TABLE I. Some American picture tube characteristics 














" flec- 









Green Screen 
White Screen 


157 8 

1,500-2,000 375-425 S-S 


Green Screen 

White Screen 







Yellow- Green 

White Screen 








White Screen 


247 2 





White Screen 

4" Projection 

147 2 20,000 




Green or Yellow- 

Green Screen 

* M-M — 



both * : 

* S = el 

ectrostatic focusing. 

S-S = electrostatic deflection both 


M = combined electrostatic and magnetic 

ture detail. As has been pointed out, 
the vertical detail resolvable in a pic- 
ture depends upon the number of scan- 
ning lines, and the horizontal detail de- 
pends upon the ability of the electrical 
system to pass extremely high frequen- 
cies. In addition to this, of course, 

frequencies, and the whole problem 
would entail development in many 
fields. To make this statement more 
striking, the band required would be 
80 times as wide as the whole spectrum 

*Ten per cent of the 441 lines must be con- 
sidered lost in the retrace interval. 

JANUARY 193 9 


now allocated to all broadcasting in the 
United States! 

Another important consideration in 
television development is the problem of 
picture brightness. Cathode-ray tubes 
used in television receivers at present, 
are as bright as could be desired in a 
darkened room. Viewed in the day- 
light, however, or even in a well-lighted 
living room, their brightness is deficient. 
While it is always possible to darken 
motion picture theatres, television re- 
ceivers will probably be expected to 
be more versatile, and to operate in 
bright bght as well. 

The problem of increasing picture 
brightness is being attacked in many 
ways. Operating voltages for instance 
can be and are being increased. This, 
however, is undesirable from the stand- 
point of safety and cost. More efficient 
luminescent materials are, of course, 
the most obvious solution, and such 
materials are constantly under develop- 

Another interesting development in 
this connection is the direct-viewing 
tube. This differs from the ordinary 
tube in that the bombarded side of the 
screen is viewed, instead of the opposite 
side, as is customary. Such tubes na- 
turally require a construction of un- 
orthodox shape. However, they may 
be the tubes of the future, both for 
reasons of brightness and also for rea- 
sons of contrast and detail, as will be 
pointed out later. Maloff reports a 
direct-viewing tube having a maximum 
useful brightness of 100 candles per 
square-foot. This is more than ten 
times as bright as the highlights in a 
high-quality motion picture. 

• Television Picture Contrast 

Finally, there must be considered the 
matters of contrast and detail. The 
present contrast available in television 
tubes is quite good, but much still 
remains to be done. For one thing a 
cathode-ray tube exhibits the phen- 
omenon of halation. This is the optical 
effect of the diffusion of light in the 
screen material, and with it we may 
also group the internal reflection of 
light from the walls of the tube. 

Halation is well known in photog- 
raphy. It decreases the brightness of 
highlights and diffusely lights up points 
which are supposed to be dark, par- 
ticularly in locations near the high- 
lights. The general effect is thus to 
f'ecrease the available contrast and to 
limit the possible fine detail. The di- 
rect-viewing tube is a very effective 
means of decreasing halation. When 
such a tube is used, the increased con- 
trast is very striking. 

In addition to halation, a cathode-ray 
tube, also exhibits the phenomenon of 
"blooming," which is an electrical effect 

and results in defocusing the spot in 
the highlights. Improved focusing ar- 
rangements can be used to decrease 
"blooming," but even in the best of 
modern tubes it still is a problem. 
Since the contrast desired in a tele- 
vision picture requires an electronic 
beam of varying density, the focusing 
of the tube must be so arranged that 
the focal point does not change with 
current density, i.e., brilliance. This 
is not an easy problem. However, it 
is evident that before 2000-line pictures 
are ever obtained, great advances must 
be made in the cure of "blooming." 

• Propagation of Signal 

The problem of signal propagation in 
television assumes an importance which, 
in many respects, is far more serious 
than that of the corresponding problem 
in sound transmission. In the first 
place, the exceedingly wide frequency 
channels required in television make it 
necessary that the signals be trans- 
mitted in the ultra-short-wave bands. At 
these frequencies, as is well known, 
there exists reliably only line-of-sight 
transmission, since there is no longer 
reflection from the Heaviside layer. 
While this fact limits the area of cover- 
age of any transmitter, it is actually 
very desirable from the standpoint of 
interference. Thus there is far less 
likelihood of multiple images caused by 
multiple path reception, due to re- 
flections from the Heaviside layer, or of 
interference from a distant station 
operating at the same frequency, or 
from atmospheric "static." The only 
serious sources of noise at these fre- 
quencies are those generators within 
approximately line-of-sight, of which 

noteworthy examples are automobile 
ignition systems and medical diathermy 

While reflections from the Heaviside 
layer are negligible, nevertheless, be- 
cause of the very short waves employed, 
objects such as steel buildings, water 
towers, overhead wires, etc., provide 
efficient reflectors and give rise to 
"ghost" images. The severity of this 
problem will be realized much more 
fully than at present when the gen- 
eral public begins the erection of re- 
ceiving antennae and the operation of 
receivers on a large scale. 

The line-of-sight limitation greatly in- 
creases the difficulty of serving a large 
geographical area with a given pro- 
gram. 46.6 miles is the radius of the 
area over which reliable coverage can 
be obtained from the transmitter, pro- 
vided that the power of the transmitter 
is sufficiently great. Consider, now what 
this transmitter power must be, in order 
to give reliable reception at the re- 
quired distance from the transmitter. 

• Power Requirements 

It is an empirical fact that reliable 
reception of a television program re- 
quires an input signal of about one 
millivolt. The required transmitter an- 
tenna power is 27.4 kw. Actually, at 
the present time it is not possible to 
radiate this much power, since no tubes 
are available to generate it at these 
ultra-high frequencies. 

Using two of the latest high-power 
developmental tubes in push-pull, it is 
possible . to generate 10 kw. (40 kw. 
peak) at fifty megacycles. The limit- 
ing factor in this case is the fact that 
the size of high power tubes makes it 

Receiver Sale Premature — Zenith Prexy 

By e. f. Mcdonald, jr. 


"The offering for sale of television re- 
ceivers at this time ... is in my opinion, 
unfair to the public and premature, both 
for economic and technical reasons. Such 
premature introduction . . . will load the 
public with undue experimental replace- 
ment cost, which in turn, will result in re- 
tarding, instead of furthering, development 
and in unprofitable operations for the com- 
panies engaging in such a program. 

"I do not believe the radio industry should 
ask the public to pay for its experimentation 
in television, at least without putting the 
public on notice that receivers put out at 
this time are on an experimental basis and 
may be subject to many costly changes and 

A 'Stock Proposition' Now 

"I still feel . . . that 'general use of 
television in the homes is just around the 
corner for the stock salesmen only.' When 
we have overcome all of our difficulties — 
and when I say we, I mean the radio in- 

dustry — television will no doubt become a 
wonderful new industry. I feel that I am 
as close to the television picture as the 
next man, and Zenith is prepared at this 
time to produce and sell television receivers; 
but I am not ready to take the public's 
money until television is . . . ready to 
provide money's worth . . . 

Obsolescence Important Factor 

"Television is essentially different from 
anything with which we have had to deal 
in the past. The first automobiles . . . 
sold to the public, unless they have been 
worn out from use, will still operate on 
our highways today, and with the gasoline 
now used. Likewise, the first radio receiv- 
ers . . . sold to the public will still oper- 
ate and reproduce programs from the most 
modern broadcasting stations of today. On 
the other hand, the television receiving set 
of one year ago is already obsolete and 
cannot be operated in the home with the 
latest television transmitter of today. 

"What the public should know, but has 
not been told, about television is that the 
receivers must be matched to, synchronized 
with and built on the same standards as 
the transmitters. Any major change made 
in the television transmitter will necessitate 
a change in the receiver." 



impossible to tune them above a certain 
critical frequency and their high inter- 
electrode capacities make it difficult to 
load them properly and still preserve 
the desired band pass characteristics. 

Thus with tubes of the present types, 
it is not yet possible to reach the de- 
sired power level; and the condition 
will become more serious as more of 
the still higher frequency channels are 
used for television. However, it is rea- 
sonable to expect that the ingenuity of 
tube designers will overcome this diffi- 
culty in the next few years. In the 
meantime, the condition can still be 
corrected by increasing the height of 
the transmitting antenna, and especially 
of the receiving antenna. 

It requires 12.9 kilowatts of trans- 
mitted power to generate a signal of 
one millivolt in a half-wave dipole 4 
meters above the ground at the horizon. 
This value is independent both of the 
carrier frequency and of the height of 
the transmitting antenna. The latter 
result is very surprising. It indicates 
that as the antenna height is increased, 
the same power still suffices to reach 
the horizon — the increased distance be- 
ing just compensated by the increased 
antenna height. 

Another problem of considerable im- 
portance in the adequate coverage of 
the line-of-sight area is the elimination 
of multiple reception or echoes. This 
problem is of practically no importance 
in sound broadcasting. To get a clear 
idea of the problem, suppose that in 
addition to the direct ray travelling 
from the transmitting to the receiving 
antennae there is also a ray which 
reaches the receiving antenna by way of 
reflection from a large building. This 
reflected ray will have travelled a 
greater distance than the direct ray be- 
fore reaching the receiver. The picture 

Academy Report on Television Progress 

REFLECTING the view of West Coast 
studio technicians anent present 
status of television is the third annual 
report of the Research Council of the 
Academy of Motion Picture Arts & 
Sciences, a summary of which is append- 
ed hereto. 

England led in putting television on a 
public service basis, inaugurating regu- 
lar transmission on Nov. 2, 1936. Has 
made notable technical progress and in 
quantity and quality of entertainment, 
but these advances have not been re- 
flected commercially. Present receiver 
sales are two sound-only sets to one vis- 
ual set (some of which include sound). 

Peak of 4,000 television receivers now 
indicated for television service area, in 
which are 10 million people. Public in- 
terest has been sustained, with probable 
extension of coverage promising much 
wider potential market. Unflagging inter- 
est undoubtedly due to visual broadcasts 
of sporting and ceremonial events, in- 
cluding the Derby, prize fights, tennis 
matches, boat races, soccer games, etc. 

Quality of televised image is nowhere 
near that of 35 mm. film projection, but 
has reached stage where it can add en- 
tertainment value to film houses. Re- 

which it carries will therefore be re- 
tarded in time, and it will consequently 
cause a similar but slightly displaced 
picture to appear next to the desired 
picture. This is a very annoying effect, 
and great effort must be made to avoid 
it. This effect is illustrated in Fig. 11. 

A path difference of 127 feet will 
cause an echo displacement of one pic- 
ture element. This is enough to detract 
from the quality of the picture. 

The elimination or reduction of 
echoes is a complicated problem. In 
metropolitan areas, due to the presence 
(Continued on page 24) 

FIGURE 4. The effect of multiple-path transmission or reflection 
upon the received image 

ceiver sets range in price from $144 to 
$756, depending upon image size. Pro- 
grams broadcast average two hours daily, 
three hours on Saturdays, and one and 
one-half hours on Sunday. Present stand- 
ard of 405 lines, 50 frames per second, 
will not be changed until end of 1940, 
thus dispelling fears of receiver obso- 
lescence until then. 

Mobile pick-up unit provided, in addi- 
tion to cable network in desirable sec- 
tions of London. Coaxial cable laid be- 
tween London and Birmingham, to be 
extended shortly to Manchester, al- 
though primarily for telephone purposes, 
may eventually be used for television. 
Television transmitter has useful range 
of 50 miles at present. 

• Developments in Germany 

Experimental station in Berlin util- 
izes same power as London transmitter, 
17 kw, with definition of 441 lines and 
frame frequency of 50 per second. Two 
other transmitters are planned. A pic- 
ture 12 by 10 feet has been shown in a 
theatre. There are reports of a 700-line 
image. Cathode-ray tubes up to 26" di- 
ameter have been built. Cost of receivers 
is said to range between $175 and $1,000, 
with $320 as an average. 

• France Relatively Inactive 

Eiffel Tower transmitter, rated at 25 
kw, more powerful than Berlin or Lon- 
don; its signals have been viewed 180 
miles distant. Station transmits daily for 
2*A hours. There are reports of a 12 by 
9 foot theatre demonstration, with qual- 
ity approaching 16 mm. projection. No 
information on receivers or extent of pro- 

• Developments in the U. S. 

RCA-NBC experimenal transmissions 
from Empire State Tower (N.Y. City) 
have continued since July, 1936. System 
uses 441 lines, 60 frames per second. 
Home television now regarded as "tech- 
nically feasible". RCA promises limited 
program service and marketing of re- 
ceivers by April 30 next. 

Receivers have screens 10 by 7/4 
inches, too small for convenient viewing, 
but pictures are bright and sharp and 
carry sufficient detail to depict emotions, 
when rather broadly played, in close-up 
or semi-close-up. Medium and long shots 
merely show the figures and are used 
mainly for entrances, exits, establishing 
settings, etc. In the main, story must be 
carried with two shots. Film takes of 
exteriors are sometimes intercut to good 

A member of Academy Research 
Council who witnessed some of the dem- 
onstrations found it difficult to concen- 
trate on engineering features — his atten- 
tion was constantly diverted to the ac- 
tion. This is as good a test of enter- 
tainment quality as any. 

Last June several N. Y. department 
stores demonstrated television reception, 
using the NBC transmissions. Pictures 
were mostly in the 5 by 4 inch range, 



with receivers priced at $195 to $225. 
Public interest was aroused, but few 
sales were reported. Flurry ended when 
transmitter shut down for adjustments. 
Real test of public response will come 
when regular service is initiated and re- 
ceivers become available in a number of 
types and sizes. 

Engineering developments in the 
U. S. parallel those abroad. Progress is 
slow and laborious, but steady. In gen- 
eral, the advances listed above for the 
foreign field are either the results of Am- 
erican invention, or they can be dupli- 
cated here whenever it becomes expedi- 

During 1939 a moderate extension of 
local television coverage is in prospect 
in various parts of the country. CBS's 
transmitter will be installed early in the 
year and begin regular operation. A 
considerable number of applications for 
experimental television licenses are on 
file with the F.C.C. 

In Los Angeles, which may reasonably 
be expected to carry over into the field 
of television its importance as a radio 
and motion picture center, a Don Lee 
station has been televising for some 
years. Present standard is 300 lines, 24 
frames per second, visual frequency, for 
about eight hours a week, both film and 
live subjects being scanned. Visual 
broadcasts of the lkw transmitter are 
received as much as 30 miles away. 

The Farnsworth system was demon- 
strated in Hollywood last summer. The 
picture was in black-and-white and about 
9 by 12 inches in size, the image being 
441 lines, 60 frames per second. The 
picture was bright and had considerable 
entertainment value on the close-ups. 
Longer shots were not as effective. 

• Research Council Conclusions 

The long experimental phase of tele- 
vision is about to culminate. The ex- 
periment now takes on a larger scope, 
with the emphasis shifting from technical 
research (although technical develop- 
ment will simultaneously be intensified) 
to economic and social aspects. The pub- 
lic, from the role of spectators, will be- 
come participants in the project, and on 
the extent and manner of that participa- 
tion the effects on the motion picture in- 
dustry will depend. 

That such effects will be evident in the 
next two years is altogether to be ex- 
pected. That the repercussions will re- 
sult in revolutionary changes in motion 
picture production and exhibition with- 
in that period is unlikely. The complex- 
ity of the television field and the magni- 
tude of its artistic and financial prob- 
lems are an automatic brake in this re- 
spect, and it might be added that this is 
true of competitive and cooperative po- 
tentialities alike. 

As regards the latter, when television 
comes into its own it may well open up 
a vast market for films especially de- 
signed for television distribution. Should 
competitive factors predominate, it is 
quite obvious that the strongest interests 
in the television field cannot afford to 
ignore their own very substantial stake 

Television and the Future of 
the Motion Picture Theatre 


[NOTE: The appended article is a summary of an address given before 
numerous projectionist Local Unions in the East.^ 

THE question most commonly asked 
by projectionists anent the tele- 
vision art is: What will television 
mean to the motion picture theatre? 
Which is just another way of asking: 
What will television mean to us, and how 
will it affect our jobs? It is exceedingly 
doubtful that anybody can give an accur- 
ate answer to this question today, al- 
though there are innumerable candidates 
for the title of "expert". All one can do 
is to present certain facts that have 
emerged from the haze of uncertainty 
surrounding the television art, dispel a 
few myths — and let the reader draw his 
own conclusions. 

This summary is shy on technical data, 
these being covered in detail in an 
article elsewhere herein. 

Beginning with pick-up in the studio, 
television is confronted by precisely the 
same problems, and more, that are en- 
countered in the motion picture studio — 
that is, questions of makeup, lighting, 
costuming, scenery, scenarios, actors and 
all the other requisites that enter into 
film production. If film be used as the 
pick-up medium, as it will be and ex- 
tensively, these studio problems natur- 
ally will not exist. (It is interesting to 
note, incidentally, that when film is used 
a Powers 5 to 1 projector movement is 
utilized, the necessity for a fast move- 
ment being obvious.) Outdoor scenes 
have already been televised, but only 
under ideal conditions. 

• Program Distribution 

Program distribution is the major 
headache of television technical workers 
at present. The permissable broadcast 
distance today extends only to the visual 
horizon, a distance of about 50 miles, de- 
pending upon the terrain. This means, 
then, that a transmitter must be erected 
every 50 miles, in all directions, through- 
out the country. Each transmitter would 
cost about $200,000 — thus providing 
great sport these winter evenings for 

those mathematically inclined. Two 
means of effecting a nationwide broadcast 
network, as it exists in radio today, are 

1. Coaxial cable, an A. T. & T. de- 
velopment, which is a wire proposition, 

2. Radio relay system, which is 
straight etherization. 

The telephone people naturally prefer 
that the coaxial cable plan be adopted; 
while RCA favors the radio relay idea. 
Of course, assuming that the nation 
were blanketed by transmitting stations 
as previously outlined (and what a task 
this would be, and at what cost!) film 
prints could be shipped to each trans- 
mitter for broadcast. Naturally, this 
would not constitute a broadcasting net- 
work comparable to existing radio net- 

It is a matter of record that the 
coaxial cable laid over a distance of 90 
miles between New York and Philadel- 
phia cost $540,000. What portion of this 
cost represents engineering development 
is not known, but we have here an in- 
dicated cost of about $5000 per mile. 
Currently the major radio networks use 
on the order of 45,000 miles of telephone 
line to hook-up network programs. Thus 
by the simple process of multiplying 
the number of miles, 45,000, by the 
cost-per-mile, $5000, we arrive at a total 
cost of a coaxial cable network hookup 
— and we find ourselves wrestling with 
an astronomical figure. The cost-per- 
mile of coaxial cable may be reduced 
sharply in the not too distant future. 

The radio relay plan is wholly feasible, 
of course, but very difficult and quite 
costly, although not approaching the 
cost of coaxial cable. So much for the 
problems incident to setting up a tele- 
vision broadcast network. Mark well 
the cost of this job, quite apart from 
the technical problems involved. 

Another extremely serious problem in 

in the business of aural broadcasting. 
Although radio is nowhere near the end 
of its growth, financially it has become a 
mature industry, mindful of its invest- 
ment in the present while looking into 
the future, and this tendency constitutes 
a protection, if one is needed, for the 
other entertainment industries as well. 

And yet, modern technology has its 
own dynamic imperatives. It will not and 
should not stand still. New industries are 
needed, and if their coming is trouble- 
some, it will be far more troublesome if 
they do not come. Television is one of 
them and it is a year nearer. 

The situation is one which calls for 
continual observation and analysis by the 

motion picture industry, and to an in- 
creasing degree r as events take their 
course. The Academy Research Council 
should immediately proceed to a more 
thorough consideration than has been 
undertaken in the past of the prospec- 
tive relationships between television and 
motion picture production and exhibi- 

This investigation should cover the ar- 
tistic, technical, legal, and economic 
phases of the subject. Therefore, the 
Committee recommends that it be en- 
larged to include representation from 
those other branches of the industry in a 
position to contribute a wider back- 
ground to its considerations. 



television broadcasting is interference, 
the reflection of so-called "ghost 
images." Automobile ignition systems 
constitute a major source of interference, 
as do overhead wires, steel buildings, 
water towers, and the like. The auto- 
mobile ignition problem could be solved 
with the cooperation of car manufac- 
turers; but the problem posed by build- 
ings, wires, etc., will sorely tax the ingen- 
uity of the best engineers. 

• Receiving Set Data 

On the reception end, we find that 
the best sets available (for example, 
those of RCA and G. E.) will provide 
an image 10 by 7^2 inches and will 
retail for about $300. These sets will 
provide an image of greenish tint with a 
rather low light level. The fluorescent 
material used in the tube will be im- 
proved, of course, but not immediately. 
It is conceded that the desirable view- 
ing distance is between 8 and 10 feet, 
which would require a picture image 
of at least 2 feet. Since the image is 
only 10^ by 7 inches (about the size 
of this page) the maximum viewing dis- 
tance is reduced to about 4 feet. This 
not only limits seriously the number of 
people who can view the image but it 
also introduces the serious question as 
to the willingness of the viewers (if 
more than one) to remain in one posi- 
tion and give fixed attention to the tele- 
vision screen for an extended period of 

Now, it is entirely possible to enlarge 
the television image, much as is done 
in a motion picture theatre with a de- 
vice such as the Magnascope. As we 
all know, however, the result of magni- 
fication is a decrease in brightness — and 
brightness is already a serious problem 
even with the present image of 10 by 
7 x /2 inches. Moreover, increasing the 
image size would necessitate increasing 
the size of both tube and console, there- 
by posing another problem. 

Another serious problem is that of 
the general level of room illumination. 
Must the room lights be extinguished 
or dimmed away down? If the answer 
be "yes," then the existing problem of 
close viewing and fixed attention is 
aggravated. Another important angle is 
that television reception is not incidental 
to normal household activities, as is 
sound reception. 

The quality of present television 
images might be classified roughly as 
follows : Close-ups — approximate the 
quality of 16 mm. home movies. Me- 
dium long shots — of fair quality. Long 
shots — of decidedly mediocre quality and 
permissable at present only for dynamic 
action shots such as prize fights, racing, 
acrobatics, etc. Dr. A. N. Goldsmith 
has estimated that the "sharpness" or 
definition of a standard motion picture 
film, as contrasted with the American 
standard 441-line television image, is 
somewhere between 1500 and 2000 lines, 
or approximately four to five times 

Refinement in the art of television is 
inevitable with the passing of time, and 
in this connection it is of extreme in- 

terest to note that any change in trans- 
mitting standards will automatically 
render obsolete all existing receivers. 
This aspect of the situation is discussed 
in detail elsewhere herein, along with 
other pertinent data relative to the status 
of the art in this country and abroad. 

Admittedly the next two years will be 
a period of experimentation and develop- 
ment in the art, with no radical changes 
in its status likely before then. There- 
after it is anybody's guess as to what 
course television will take. It is en- 
tirely safe to say, however, that the big- 
gest problem confronting television to- 
day is an economic one, technical prog- 
ress having reached the stage where 
regular programs could begin tomorrow 
if sufficient transmitters and receivers 
were available. The pressing question 
of the moment is: Who will foot the 

Network sound broadcasting today 
costs about $30,000 an hour. It is esti- 
mated that an elaborate motion picture 
play, produced along typical Hollywood 
lines, would add to this figure an addi- 
tional cost of $25,000 a minute! while 
the worst picture that any audience 
would tolerate would cost an additional 
$1,000 a minute. No such circuit of 
first- and subsequent-runs as exists in 
the motion picture field today would be 
possible; once a film production had run 
its course of television broadcasting for 
about 80 minutes, it would be a cold 
turkey, finished for all time. 

Television, of necessity, has a vora- 
cious appetite for material. It is esti- 
mated that the present yearly output 
of all Hollywood studios would sustain 
a television network for only three 
months, indicating a quadrupling of film 
studio output to maintain the art on a 
broadcast schedule such as is adhered 
to in radio today. Herein lies Holly- 
wood's great opportunity not for sur- 
vival but for progress on a scale hitherto 
undreamed of — that is, if the producers 
keep their eyes peeled and are not 
blocked out of the play either by un- 
preparedness in general or, specifically, 
by those peculiar clauses in their sound 
recording contracts with the electrics 
which restrict the use of any picture 
the sound for which was recorded on 
their systems. This means in simple 
language that such pictures cannot be 
used for television. 

• Public Expects Quality 

Persistent and colorful publicity re- 
citing the wonders of television have led 
the general public to expect extra- 
ordinary things of the art — not only in 
the way of quantity in the form of long 
daily schedules, as in radio today, but 
also quality as to size and content of 
the image. Keen disappointment will 
ensue when the general public discovers 
that the television image is not 2 feet 
but rather less than 1 foot. It is all 
very well to say that novelty will sustain 
the art in its early stages, but this wish- 
ful thinking will evaporate should the 
"early stage" lengthen into months or, 
possibly, a couple years. 

Once a television service is launched, 

not even staggering costs, insufficient 
support by advertisers, or definite lack 
of interest on the part of the public 
will justify any discontinuance of the 
broadcasts, or even a "temporary" sus- 
pension. The television people under- 
stand this requisite perfectly well, which 
is why they insist that the art be ushered 
in full-blown, so to speak, and maintain 
a steady pace. 
• Effect on Film Theatres 

But what of the effect of television 
upon the motion picture theatre? The 
writer has never subscribed to the 
opinion that television will be utilized 
in theatres. It is his opinion that tele- 
vision, like the present radio broadcast- 
ing, is strictly a product for the home, 
because this is the only possible way 
in which the broadcasters can interest 
advertisers, who, after all, are expected 
to pay the freight. Why, the writer 
often asks, should anybody go to a com- 
mon gathering place, such as a theatre, 
to witness a television program that can 
be viewed with much more comfort right 
in the home? Possible exceptions to 
this premise would be the interpolation 
in a film program of televised spot news 
of widespread interest, particularly of 
sporting events. But a straightaway tele- 
vision theatre? Never! There is no 
valid reason for it. 

If this estimate be correct, then the 
competition for patronage will lie be- 
tween the motion picture theatre as such 
and television in the home. Consider- 
ing the difficulties which beset the prog- 
ress of television as enumerated herein, 
it is extremely doubtful that the art will 
enjoy any considerable audience for a 
couple years at least. After that the 
issued will be joined. But television 
positively is not the ally of motion pic- 
ture exhibition — far from it — anymore 
than radio is an ally today. In fact, 
both of these arts are stiff competitors, 
due in large part to the stupidity of an 
industry which permits its ranking talent 
to clutter up the air waves nightly, to 
the number of 24 of a recent Sunday. 

The motion picture theatre, to sur- 
vive as such, must remain just that and 
must be the beneficiary of drastic 
overhauling of the present industry 
structure and modus operandi — begin- 
ning in Hollywood. Double features 
should be eliminated in the interests of 
fewer but very much better pictures. 
The Hollywood economic setup must be 
radically revised, particularly with re- 
spect to star salaries and the nepotism 
that is rife in that alleged citadel of 
culture. Payment of $150,000 per pic- 
ture and more to individual performers 
who don't draw even flies to the box- 
office must be stopped, so that picture 
costs can be slashed. 

Distribution methods should be over- 
hauled. Distributors should stop rob- 
bing exhibitors on percentage pictures. 
In what other industry in the world, out- 
side of the prize fight racket, is a com- 
modity offered on the basis that a dis- 
tributor reserves the right to pry into 
a retailer's business and exact a given 
(Continued on page 22) 

JANUA R Y 19 3 9 


Technical Data On New RCA Sound Systems 

SIX new sound reproducing systems, 
which incorporate more than a 
score of technical advances, have 
been announced by RCA Photophone. 
Tone quality that imparts "studio pres- 
ence" to the reproduction, greater con- 
venience of operation and streamlined 
functional design are some of the im- 
provements ascribed to these equipments, 
which are the culmination of more than 
a decade of research and development. 

The new equipments have been de- 
signed to fit the sound reproducing re- 
quirements of every size and type of 
theatre, ranging from super-theatres 
down to the smallest neighborhood 

To Photophone's famed rotary stab- 
ilizer has been added a shock-proof drive 
mechanism; together they insure per- 
fectly constant film speed past the re- 
producing photo-electric cell, thus elim- 
inating any possibility of distortion from 
this source. A double exciter lamp unit 
provides an emergency spare lamp for 
instantaneous changeover in case of 
failure. The optical focuser on the new 
equipments are securely locked into 
place after adjustment. Gear failures 
are virtually eliminated by an integral 
gear box assembly built into the new 
soundheads which keeps gears running 
in an oil bath. 

• Quality, Utility, Durability 

All housings for the soundhead, amp- 
lifier racks and volume control box have 
been completely restyled, evidencing a 
new functional streamlining which not 
only improves the appearance of the 
equipments tremendously but also as- 
sures the utmost utility of every com- 

The new sound systems have been en- 
gineered, designed and built to set new 
standards of quality as well as of oper- 
ation and convenience. Standby facil- 
ities have been provided to relieve the 
fear of possible breakdown. Both the 
styling and improved operating conven- 
ience should be especially welcomed by 
projectionists. Double appeal is exerted 
by these new systems: to the ear and 
eye through outstanding performance 
and appearance; and the kind that is 
built into the apparatus to give depend- 
able, trouble-free service over its full 

Photophone hails the shockproof drive 
for the constant-speed sprocket shaft as 
its most important laboratory develop- 
ment since the introduction of the rotary 
stabilizer. The new drive makes it im- 
possible for gear backlash to be trans- 
mitted to the constant-speed sprocket, 
thus insuring absolute constancy of film 
speed. The drive mechanism is mounted 
in the new type of integral gear box 

in such a way that it can be removed 
easily as a unit for servicing or replace- 
ment. The sound bracket assembly, in- 
cluding the optical system and the drum 
shaft, can also be removed in one piece. 
An improvement which will be favored 
by projectionists is the double exciter 
lamp. If one light fails, it is only nec- 
essary to turn the socket around, and 
the spare bulb goes into operation im- 
mediately, while the burned-out one can 
be renewed as the show continues. 

• Other Important Advances 

RCA points to the new self-locking 
focal adjustment mechanism as a long 
step toward improved operation. A light 
shield in front of the optical system 
avoids 96-cycle hum resulting from mod- 
ulation of the sprocket holes in the film. 
A new type of pre-focused exciter lamp 
bulb has been utilized, doing away with 
the necessity for adjusting the lamp lat- 

The new soundhead has a smartly 
styled housing over the electric driving 
motor, giving the equipment a clean-cut 
appearance never before achieved. This 
cover, like all the others on each piece 
of equipment, is easily removed for in- 
spection or servicing. On the right side 
of the soundhead is a glass window 
which permits a view of the interior. It 
is illuminated at the edges, eliminating 

The new Photophone amplifier rack 

is trim and compact and provides easy 

access for checking or repairs 

glare and permitting a clearer view of 
the interior. 

The photo-electric cell transformer 
has been entirely shielded in a cast iron 
chamber in the soundhead, insuring vir- 
tual absence of noise from static in the 
soundhead, another improvement new to 
this equipment. 

A completely new system of mount- 
ing the picturehead in the soundhead 
has also been devised. A separate re- 
movable plate is provided atop the 
soundhead to which the picturehead is 
fastened. It is then only necessary to 
remount the removable plate on the 
soundhead, securing it with four screws 
on the outside. This contrasts with the 
older method of running long unhandy 
bolts from the picturehead into the 
soundhead. The removable plate also 
serves as an oil collection plate, gather- 
ing oil drips from the picturehead and 
feeding them into a tube which empties 
into a removable container. 

The mounting plate is also designed to 
provide easy adjustment of the picture- 
head in relation to the soundhead for 
the proper meshing of the former's 
drive gears. 

The price range of these new RCA 
systems is: for theatres of up to 800 
seats, Model 138, $1375; up to 1200 
seats, Model 139, $1650; up to 1800 
seats, Model 140, $2250; up to 2600 
seats, Model 141, $2850; up to 3800 
seats, Model 142, $3375; and for houses 
up to 7000 seats, Model 143, $3800. 


Harry M. Brooks, well-known in national 
I. A. circles, has been elected Illustrious 
Potentate of Oriental Temple, A.A.O.N.- 
M.S., of Troy, N. Y. Brooks is now serv- 
ing his 29th term as President of Local 285, 
Troy, is a former member of Local 29, a 
past-president of the N. Y. State Assoc, of 
Projectionists and present Sec.-Treas., in 
addition to serving on the 10th District 
legislative committee. He trouped for 12 
years as a stage carpenter. 


This isn't a news item, but we print it 
every year simply for the record. Thad 
Barrows and Jimmy Burke have been re- 
elected president and business represent- 
ative, respectively for their 21st consecutive 
terms. Other officers of Local are Bernard 
McGaffigan, vice-president; Al Moulton, 
financial secretary; Joe Rosen, treasurer; 
and to the executive board: Louis Pirovano, 
Joseph Nuzzelo, John Diehl, and James 


Dufaycolor, Inc., which on Jan 1 passed 
from English hands to exclusive operation 
and management by a private financial 
gioup in the U. S. will henceforth conduct 
business under the name of Dufaycolor Co., 
Inc., with offices at 30 Rockefeller Center. 



1. The new integral gear box assembly which 
keeps the gears in the new Photophone sound- 
head running in an oil bath and makes gear 
failures virtually impossible. An oil indicator 
tells the projectionist when additional lubricant 
is required. 

2. This is the mechanism which provides 
the new shock-proof drive for the rotary stabilizer 
in the new soundhead. Isolation of the constant- 
speed sprocket shaft and drive gear from the gear 
train and driving apparatus prevents gear back- 
lash from being transmitted to the constant-speed 
sprocket. Absolute constancy of film speed is 
therefore assured. 

3. The RCA rotary stabilizer which is an 

integral part of every Photophone soundhead r 
Its efficiency has been increased still further in 
the new sound systems by the use of a new 
shock-proof driving mechanism which isolates 
the stabilizer itself from all vibration or gear 
backlash. Film flows smoothly and steadily past 
the light source. 

4. Two new developments in the Photophone 
soundhead are shown here. In the front is the 
double exciter lamp socket, which makes a spare 
lamp ready for immediate use by simply revers- 
ing the socket. Also shown is the mechanism 
for focusing and locking the optical system 
(right). The lens can be focused quickly and 
accurately by the projectionist and then locked 
securely in place. 

Television and the Motion Picture Theatre 

(Continued from page 19) 

portion of the latter's income as against 
a minimum flat guarantee? But do the 
distributors offer to make up the def- 
icits of the innumerable "ham" pictures 
of B, C, D, E and F grades? 

The exhibitor just must be given a 
chance to make some money so that he 
can refurbish his house, employ the best 
mechanical facilities, better sell his film 
program and do in ever so much better 
fashion the many other things essential 
to the successful conduct of a theatre. 

More money must be alloted to the 
industry's technical forces so that pic- 
tures can be improved. Strenuous 
efforts should be made to improve color 
films and to bring out of the labora- 
tories new developments — such as stereo- 
scopic motion pictures — to the end that 
the industry may be better armed to 
fight for its share of the entertainment 
dollar. Someone well versed in both the 
motion picture and electronic arts (the 
writer can think of no better nominee 
than Dr. A. N. Goldsmith) should be 
appointed to look into the technical, 
economic and legal aspects of the re- 
lationship of motion pictures to tele- 
vision. This is a "must" procedure. 

The exhibition field must be accorded 
every aid in what will develop into a 
battle for its life. If the aforementioned 
steps are not taken, and shortly, the 
film theatre field is doomed. 

The opinion has been advanced that 
man being a gregarious animal is an 
important factor in the theatre's favor 
in its battle for patronage against visual- 
sound broadcasting. Certain it is that 
people will not be expected to huddle 
around a television receiver in a semi- 
darkened room and give fixed attention 
to a comparatively small moving image 
hour after hour, night after night; but 
it cannot be denied that anything that 
tends to keep people in the home is 
bad medicine for film theatres. Watch 
a few box-offices these Sunday and 
Thursday evenings. 
• Opportunity for Labor 

The greatest enemy of the film theatre 
today, apart from the policies pursued 
by the industry itself, the writer holds, 
is bridge. Before you laugh just stop 
and consider what a hold this strictly 
home game has on millions of people 
in this country. Next in order as box- 
office poison are the innumerable chance 
games flourishing in many cities, in the 
very forefront of which are the churches 
which resound to pious platitudes Sun- 
day morning anent the evils of the flesh 
and gambling, while in the evening the 
walls echo and re-echo to the lingo of 
Bingo and Bango. Just as an example, 
in the city of Cleveland the nightly 
Bingo games are estimated to draw an 
attendance of about 70,000 nightly, with 
games running rampant in every block. 

Such things as this are the concern 
of everybody in the industry, and a con- 
ference of producers, distributors, ex- 

hibitors and Labor to consider how best 
to attack the problems posed by all 
forms of box-office poison would be not 
at all amiss. 

Projectionists and stagehands should 
do all right in the television field itself. 
Television, if handled properly, is just 
a wooly lamb ambling down the street 
and just waiting to be shorn. In Radio 
City, New York, there are today six 
motion picture projectionists employed. 
Since motion picture film will be ex- 
tensively used in television broadcasting, 
it seems safe to say that there will be 
about 3000 projection jobs in television 
stations: and on a three-shift basis this 

number may run as high as 5000. This 
is plenty of jobs in any language. How 
this angle develops will depend in large 
measure upon how swiftly and efficiently 
Labor moves in upon the television field, 
a topic which is not for discussion 
herein. Nobody in the television field 
will say "No" to Labor, because the 
stakes are too big. 

To repeat: What will be the effect of 
television upon the motion picture thea- 
tre? The writer's opinion is that, after 
two years or so, it assuredly will do the 
theatre field no good, but the extent 
of the damage can be held to a very 
small total if only the picture industry 
will bestir itself promptly to save its 
own life. In short, the answer to the 
foregoing question is in the lap of the 
picture industry itself, from the most 
noted producer in Hollywood right down 
to the doorman of a small-town theatre. 

Wall St. Estimate of 1939 
Film Business Prospects 

The Wall Street Journal in its yearly fore- 
cast edition dealt extensively with the film 
business. Key sentences from the leading 
article : 

"The movies probably will have a much 
more profitable year in 1939 than in 1938, 
which might be called a year of expiation." 

"... the combination of lower expendi- 
tures and higher income probably will result 
in first half profits nicely ahead of a year 

"It begins to look as though a lengthy 
process of revamping and readjustment of 
policies and methods of doing business is 
just beginning to get under way." 

"Hollywood has made the error of be- 
lieving that money can be used as a substi- 
tute for brains, talent and hard work." 

"The industry is also probably carrying 
the load of too many pictures." 

"Another trend that may have important 
influence on the industry is the growing 
movement toward producing good Class B 

Favor Theatre Divorcement 

"... it is interesting to note that last 
year the only producing companies that 
made substantial profits from the film di- 
vision of their business were those that had 
the fewest theatres." 

"It may be assumed from this that thea- 
tre chains are not essential to the effective 
operation of a film producing company and 
that the industry might be benefited in the 
long run by the divorce of the production 
and exhibition divisions." 

"At least one management is understood 
to be perfectly willing to separate these two 
divisions, and eventually may take action 
along this line, even if not compelled to 
by the courts." 

Erpi Foreign Department Deal 

on all Room Equipment 

Negotiations are in progress between 
erpi and leading American manufactur- 
ers for the distribution, by erpi's for- 
eign distributing companies, of complete 
projection room equipment in approxi- 
mately fifty foreign territories. "Be- 
cause of a pronounced tendency on the 
part of exhibitors in foreign countries 
to prefer transacting business with some 
one establishment when purchasing such 
equipment," the announcement states, 

"Erpi will begin distributing a complete 
line of projectors, lamps, screens, con- 
verters, etc., American manufacture. In 
the past our foreign organizations have 
handled only W. E. sound equipment, 
but expediency has caused us not in- 
frequently to handle other kinds of pro- 
jection equipment." 

G. E. Process Removes Glare, 
Reduces Light Loss 

Glare from reflected light, which has 
made it difficult to see pictures framed under 
glass at certain angles, has been removed 
by a new process developed by General 
Electric. Similar results are obtained any 
place where glare is caused by light reflec- 
tions on glass. The process still is in a 
laboratory, stage. 

The refractive index of any type glass 
is easily determined. This known, the pro- 
cess consists of building or attaching to the 
glass a very thin transparent film of about 
four millionths of an inch, or exactly one 
quarter wave-length of light, in thickness. 
As light falls upon the film, rays are re- 
flected from both the upper and lower sur- 
faces. With the film exactly one quarter 
wave-length in thickness, those rays coming 
from the outer or upper surface are equal 
in intensity and opposite in phase to those 
rays reflected from the lower surface, thus 
counteract one another and no light is re- 

We can measure or determine the exact 
thickness of the film at any time, although 
it may be thinner than any substance we 
know of today, by an optical process. 

See Widespread Application 
The non-glare treatment of glass also 
promises to have a wide spread application 
with all other type lenses. It is commonly 
known that reflection from the surface of 
any lens causes from 4 to 5 per cent loss 
in the light transmitted. Since this is true 
of both front and back surfaces, there is 
a light loss of at least 8% in each lens. 
With some of the better type cameras, using 
three or four lenses, the loss of light reach- 
ing the plate or negative is 25 to 35%. 
With telescopes and submarine periscopes, 
where a larger number of lenses and prisms 
are used, the light loss is still greater. In 
some periscopes it is as much as 75%. 

With the exception of the slight loss by 
absorption in the glass itself, the film-treated 
lenses would transmit 100 per cent of the 
light. In an actual laboratory test, a piece 



of glass was treated and by doing so we 
increased the light transmission from 92% 
to 99.2%. 


Seventy-seven per cent of all women 
think movies are becoming more entertain- 
ing, it was disclosed in a nationwide survey 
by the Ladies' Home Journal. No movie 
during 1938 was offensively vulgar, 89 per 
cent of all women declared. 

Women as a whole were evenly divided 
on the question of whether movies should 
show scenes of women drinking, but 66 per 
cent of the farm women and 62 per cent of 
the small-town women did object to such 
scenes. There was a similar difference of 
opinion on movie scenes of women smoking. 
While 62 per cent of all women had no ob- 
jection, 57 per cent of the farm women and 
50 per cent of the small-town women dis- 

Ninety-one per cent thought children 
under 14 should be allowed to go only to 
recommended movies, and 69 per cent would 
not permit them to see more than one movie 
a week. By a small majority — 57 per cent 
— American women said there was no ob- 
jection to having advertising of products 
shown on the screen. 


Stanley Co. of America, subsidiary of 
Warner Bros. Pictures, reported a net profit, 
after all deductions, of 12,063,703. 

Technicolor reported a net profit for 1938 
of $1,200,000, more than double that of 
1937. Yearly dividend was $1. 


Two men shift legislation has been intro- 
duced in the legislatures of New York and 
Connecticut. The N. Y. bill, applicable 
only to the four first-class cities in the 
State, also provides for the exclusion from 
the projection room of all persons other than 
licensed projectionists while equipment is 
operating. Sixth consecutive try for the 
Conn. bill. 


Motion Pictures Greatest Year Campaign, 
including $250,000 Movie Quiz Contest, is 
generally regarded as the biggest egg ever 
laid in the industry, judged from any angle, 
but particularly from that of box-office 


Theatre sound servicemen were taken into 
Detroit Local 199 for the first time recently. 
Batch inducted numbered seven men em- 
ployed by Altec and RCA. 


Officers of American Projection Society, 
of N. Y. City, for the ensuing year are: 
Pres., E. McD. Bendheim; v.-p., A. R. 
Bishop; Sec, F. McMahon; Treas., J. 
Ambrosio; Sgt. Arms, J. Chulchian. Board 
of governors is A. Polin, E. Ferris, E. 
Levene, F. D. Sm,ith, T. Rugino. The 
A. P. S. was the first technical organization 
in the field, being organized in 1914. 

P. A. McGuire, long an honorary mem- 
ber of the Society, for the sixth consecu- 
tive year installed the officers. 


Capitol Motion Picture Supply Corp. of N. 
Y. City has just observed the twentieth an- 

Read These Reasons — 


Tops the Field Because — 


It Offers 

Better screen illumination regardless of make, size and type — Minimum cost 
in current and carbons: MORE LIGHT PER AMPERE!— Maintenance is 
negligible — Every lamp guaranteed mechanically for one year — Has every 
known proved improvement — Modern and simple to operate — Costs no more 
than lamps of inferior quality — Guaranteed by the oldest and largest manu- 
facturer of projection lamps — Practical for either the 500-seat or 5,000-seat 

At Independent Theatre Supply Dealers Everywhere 
In Canada: Dominion Sound Equipments, Ltd., Montreal, Quebec 


47-31 Thirty-Fifth St. 

Long Island City, N. Y. 

niversary of its founding. Under the direc- 
tion of I.. Perse, this house has served pro- 
jectionists and exhibitors efficiently and 
equitably, its major concern having been 
and continues to be the prestige of its name. 


Installation of visual and sound projection 
facilities in all office buildings, modern or 
otherwise, is forecast by Eric W. Haldenby, 
prominent Canadian architect, as an aid to 
modern merchandising. Air-conditioning 
and sound-proofing having only recently 
gained widespread recognition as aids to 

greater human efficiency, said Mr. Haldenby, 
it is only natural that business should ex- 
plore the electronic arts as a further step 


J. Frank Brockliss, 59, internationally 
known distributor of motion picture equip- 
ment died recently in London, England. 
Formerly engaged in film distribution with 
Metro-Goldwyn and with First National in 
London and in Paris, Brockliss in recent 
years devoted all his time to the supply 
house which he founded. 



Mr. Projectionist: 

Knowing that the TRANSVERTER maintains its 
efficiency uniformly year after year . . . why 
even consider other equipment that requires 
nearly total replacement within five years? 

Sold through The National Theatre 
Supply Co.; In Canada, General 
Supply Co.; or write 





12692 Elm wood Avenue 


Cleveland, Ohio, U. S. A. 

Exclusive Manufacturers of the Transverter 


(Continued from page 17) 

of many reflectors in the form of tall 
buildings, the problem is serious indeed. 
The usual solution is to use a direc- 
tional antenna which will discriminate 
against the undesired signal. Horizon- 
tal polarization of the radiated signal 
has been found to improve the signal- 
to-noise ratio at television carrier fre- 
quencies, and its use will therefore 
probably become a standard practice. 

• Network Problems 

Some of the problems connected 
with the chain distribution of television 
programs may now be considered. There 
are two general methods which have 
been used to transmit television pro- 
grams from a key transmitter to a dis- 
tant transmitter. These are the use of 
(1) The radio relay or (2) The coaxial 
(or other) high-fidelity cable relay. 

Whichever method is used, the relay 
stations must be sufficiently close to- 
gether so that non-fading, noise-free 
signals are received at each repeater 
location. It has been found that relay 
stations must be located from 30 to 70 
miles apart, the exact distance depend- 
ing on noise conditions and (in the case 
of the radio relay) on the topography 
of the landscape. It has been cus- 
tomary to operate radio relays at wave- 
lengths of two meters or less. Each 
relay station, of whichever type, must 
reproduce the incoming signal with the 
highest fidelity, having neither ampli- 
tude, frequency, nor phase distortion. 
In other words, the picture must not 


be degraded in passing through the re- 
• Major Problem is Cost 

It is not surprising that the great 
problem in the relaying of television 
signals is cost. The cost-per-mile of a 
coaxial cable required to handle the 
exceedingly wide frequency bands of 
television programs is, at the present 
time, many times as great as the cost 
of corresponding networks used in sound 
broadcasting, both as regards initial 
cost and maintenance. If radio relay- 
ing is used, the cost of the relay trans- 
mitters required is obviously very great. 
However, the coming years are likely 
to bring great reductions in the costs 
of both methods of relaying, particularly 
the coaxial cable. 

This paper has been an effort to point 
out the fact that many problems still 
must be solved before fully satisfying 
television pictures will be available in 
the home. However, it is not to be 
construed that the commercial introduc- 
tion of television will await a solution 
to these problems. Undoubtedly tele- 
vision will be commercialized in the 
near future and the problems will be 
solved as time passes — much the same, 
for instance, as was the case in the mo- 
tion picture industry. One fact is very 
clear, that the further development of 
television must come largely through 
findings in the field, that is, by actual 


Mr. McNabb: Referring to the repro- 
ductions of a British picture and an Ameri- 
can picture, the line structure was quite 
evident in the British picture, but the con- 
trast seemed a little better. Is the con- 
trast better in the British picture due to 
the method of transmission, or is the trans- 
mission of direct current along with the 
signal better than the American method of 
adding the d.c. at the receiving end? 

Mr. Kaar: There is no essential differ- 
ence in the method of transmission in 
England and here. The only difference is 
the means of synchronization. As far as 
contrast and detail are concerned, there 
should be no difference between the two 
systems except for the possible fact that we 
have 441 lines whereas they have 405. 

It is possible to photograph any kind of 
picture from the front of a picture tube 
and we can so adjust focus and contrast 
as to make the line structure visible on 
an American picture. 

As a matter of fact, neither of these pic- 
tures is a good example because they have 
both been degraded by photographic proc- 
esses in the original photograph, the en- 
largement, the negative, and the lenses, so 
in order to compare the two fairly the orig- 
inals should actually be seen. Our pictures 
are somewhat better than the British pic- 

Mr. Finn: In the choice of repeaters, 
Mr. Kaar suggested that the choice as be- 
tween coaxial cables and straight etheriza- 
tion of a program is very close. Is it your 
suggestion that the coaxial cable be used, 
over hill and dale for thirty or sixty miles, 

$i£?mie SMS- 


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throughout the whole broadcast circuit, to 
bJanket the country? 

Mr. Kaar: That is a difficult question 
to answer because I am not familiar with 
the recent progress on coaxial cable. You 
will find a description of the New York- 
Philadelphia cable in the literature. As I 
remember, it has repeaters every ten miles 
and as yet will not transmit the full band 
required. Perhaps some day transcon- 
tinental cables may be laid capable of 
handling television programs, but I can not 
say that they will. The other system is 
satisfactory and has been tried. As to the 
economic balance between the future use of 
cables and ether channels, that still remains 
to be answered. 

Mr. Goldsmith: The New York-to-Phila- 
delphia cable was said to have cost $540,- 
000. Whether that included large engineer- 
ing developmental expenses or not, it is not 
known. In any case, that would have in- 
dicated a per-mile cost of $5,000 or $6,000. 
The major broadcasting networks in the 
United States today use somewhere on the 
order of 40,000 or 45,000 miles of lines, 
and if one multiplies that by $5,000 for the 
cost of laying a similar coaxial cable net- 
work, the result of the multiplication is an 
extremely large and uneconomic amount. 

However, it is believed that development 
will lead ultimately to less costly coaxial 
cables with repeater stations closer together 
and satisfactory for the purpose, or to eco- 
nomic radio relay systems that will work 
very effectively. 

Mr. Kaar: The fact that such a serious 
problem exists in chain programs comes 
pretty close home to the motion picture 
engineer, because for the immediate present 
there is an answer to the chain broadcast- 
ing of television programs, namely, the 
transmission of motion picture films, which 
will undoubtedly be done extensively. 

Mr. Goldsmith: There are many prac- 
tical and artistic reasons why film will 
necessarily be widely used. 

Mr. Williford: Does the adoption of 
the 60-cycle frequency as standard mean 
that communities having 25- or 50-cycle 
power supply are definitely out of the pic- 
ture as far as television is concerned? 

Mr. Kaar: There is no connection be- 
tween the synchronizing mechanism of tele- 
vision and the power frequency. The syn- 
chronizing is accomplished by transmitted 
signals. The only reason and the advan- 
tage of choosing a frame frequency that is 
a multiple or submultiple of the power-line 
frequency is this: If a system should de- 
velop a ripple, as we know it in audio 
work, that ripple would occur at power-line 
frequency. If the frame frequency occur- 
red at some other frequency than that, this 
ripple, which would be either a light area 
or a dark area, would travel across the 
screen. If the system is perfect and there 
is no ripple, it makes no difference at all. 
This is simply chosen as a safety measure. 

Mr. Goldsmith: If the power-supply sys- 
tem of the receiver and its shielding are 
so engineered that no such effects appear, 
the receiver can be used equally well re- 
gardless of the power supply. 

Mr. Cable: It seems to me that the fre- 
quency chosen as 30 places a definite 
limitation on the picture brightness, be- 
cause frequency is a function of brightness. 

Mr. Goldsmith: The present standard 
is 60 pictures per second. We see 60 "half 
pictures," with interlaced scanning. First 
is shown a picture with lines 1, 3, 7, and 
so on, as a full picture; and the one with 
lines 2, 4, 6, 8, and so on, as the next 
picture, a sixtieth of a second later. So 
the frame frequency is 30 but the field fre- 


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quency is 60 per second. You substitute 
for picture flicker a new effect called inter- 
line flicker, which is practically invisible. 

Mr. Friedl: I see a lack of uniformity 
among the standards adopted by Germany, 
Great Britain, France, and America. In- 
asmuch as the number of lines selected is 
441, which has been selected mainly to 
allow room for improvement, can not we 
look forward to transmission across the 
ocean, and, therefore, international stand- 

Mr. Goldsmith: We may hope for this, 
because some such standard as 441 lines 
for the picture might be adopted by all the 
nations. But it must be admitted that at 
the present time radio differs from motion 
pictures in that international standardiza- 
tion is rather conspicuously absent. 

Mr. Friedl: We are conscious of the 
high voltages in the larger tubes — 25,000 
and 40,000 volts. What is the voltage on 
the 12-inch tube and how does the system 
meet with the protective requirements of 
the NFPA and the Fire Underwriters? 

Mr. Kaar: The voltage on the 12-inch 
tube will probably be 6000 volts. That 
sounds like a very serious matter, but 
really it is not. If you sit in a dentist's 
chair and he turns the X-ray on you, that 
is about 40,000 volts. It is protected. It 
simply means we have a job of protecting 
the television receiver, possibly by an inter- 
locked back. 

Mr. Friedl: All I can say is that con- 
ditions in the home where children might 
come in contact with the apparatus are 
different from what they are in a dentist's 

Safety Features of Console 

Mr. Goldsmith: The back of the re- 
ceiver is expanded metal mesh. If you 
open the back, you will open all power cir- 
cuits and discharge the high-voltage con- 
densers automatically. If you try to take 
the cathode-ray tube out you will similarly 
open up the circuits. You can not get into 
contact with a high voltage. It is generally 
so arranged that even people with screw- 
drivers and determination simply can not 
get into trouble, and we hope these prac- 
tices will continue. 

Mr. Friedl: Does horizontal polarization 
mean that the antenna will be horizontal? 
Also, is that discussion of a three-meter 
receiving antenna going back to a multi- 
plicity of "wash line" antennas on every 

Mr. Goldsmith: The antenna wire or 
rod is only about six feet long. The two 
component rods are each about three feet 

Mr. Kaar: They are half a wavelength 

long, and the wavelengths are of the order 
of five meters. 

Mr. McNabb: It was the opinion of cer- 
tain American engineers who investigated 
the British pictures that the British were 
ahead of us in their technical developments 
as well as their commercial exploitations of 
the art. That seems to disagree with the 
opinions of other American engineers. Ex- 
actly what are we to believe? 

Mr. Goldsmith: The consensus of en- 
gineering opinion among those who have 
seen television pictures in London and New 
York is that there is little if anything to 
choose between them. It is most unlikely 
that practice in either case is far ahead of 
the other. 

Twelve projectionists either burned to 
death or permanently disabled is 1938's 
record in a "non-hazardous" occupa- 
tion. Oklahoma courts please note. 

• • • 

Comes now after all these years a 
group which repeatedly requests that 
I. P. reconsider on the basis of pres- 
ent performance its disapproval of Mir- 
O-Guards. We'll do it; with publica- 
tion of our findings to follow, as usual. 

Gradationally Perforated 

Tests show that a serious loss of 
fight begins one-third of the dis- 
tance from the center of the pic- 
ture area and increases sharply 
to a light loss greater than 33 1/3% 
at the sides. This loss Is elimin- 
ated in the Even-Lite Screen. 


Exclusive Sales Agents 


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All take-ups wind film on 2, 4 or 5 inch hub reels. 

The Clayton Rewinder 

For perfect rewinding on 2000-foot reels. 


31-45 Tibbetr Avenue New York, N. Y. 








Get spare photocells for 
every projector. Order 
from your supply dealer! 


1731 Belmont ■ Chicago 


Visitron cells are available for every type of sound projec- 
tion equipment. Theatre supply dealers can advise the 
correct cell for your equipment. Buy from your supply 
dealer. For information on checking the efficiency of old 
photoelectric cells, write direct to G-M Laboratories, Inc. 




We will be very pleased to send you copies of letters from many Theatre Owners who say 
— "Public reaction to Simplex Four Star Sound System is 100% favorable." "Simplex Four 
Star Sound System has made a good impression on our patrons." "Simplex Four Star Sound 
System has met the praise not only of the lay patron but also the Sound Engineers from 
the Major Studios in Hollywood." "Hundreds of patrons volunteer complimentary remarks 
regarding Simplex Four Star Sound System." 





AMD / 





! $£g!CAL D£i£ 





25c A COPY • $2 A YEAR 






Get spare photocells for 
every projector. Order 
from your supply dealer! 

1731 Belmont * Chicago 


Visitron cells are available for every type of sound projec- 
tion equipment. Theatre supply dealers can advise the 
correct cell for your equipment. Buy from your supply 
dealer. For information on checking the efficiency of old 
photoelectric cells, write direct to G-M Laboratories, Inc. 

That's what you'll 

say when you 

see it! 

Here's the finest movie sound in 
the world— created by RCA Pho- 
tophone engineers for you! And 
you don't have to take our word 
for it— just ask anyone who's seen 
it— or, better yet, see it yourself! 
It assures constant film speed 
by adding the ingenious new 
Shock-Proof Drive as a "partner" 
for the great Rotary Stabilizer. 
It offers new styling... new con- 

venience. protection. 
added reserve power! 

And that's not all! Look at the 
many other features at right! Add 
them all up and they mean sound 
such as you never before have 
been able to present to your 
audiences! The kind of sound 
that spells the biggest box-office 
ever! Get full details from your 
RCAPhotophone representative! 

1 Push-pull adaptability 

2 High frequency cellular 

3 Large size, low frequency 

4 Emergency stand-by 

5 Tube testing meter 

6 Pre-focused exciter lamps 

7 Front wall volume control 

8 Accessibility 

9 Simplified inner apparatus 


10 Economical operation 

11 Low cost maintenance — 

liberal service 

12 Easy payment plan 

RCA presents the Magic Key every 

y, 2 to 3 p. m.,E.S. T., 

NBC Blue Network 


In 1934 a group of engineers looked into the fu- 
ture of the motion picture industry. They were plan- 
ning a copper oxide rectifier for projection service. 
The foremost thought in their minds was that you 
fellows must be freed from the fear of frequent de- 
sign changes if you are to buy the equipment you 

The result of this careful planning was the con- 
servatively-designed G-E Copper Oxide Rectifier for 
Motion Picture Projection Service. 

Its designers gave you the 3-unit transformer for 
greater efficiency. They remembered that you wanted 
a minimum of operating noise and heat, so they pro- 
vided for it. A remote control system was added to 
enable the rectifier to be controlled from the lamp 

pedestal. Control of the rectifier was so simplified 
that the simple opening and closing of the 110-volt 
control circuit was sufficient to start the blower 
motor, close the relays, and automatically connect 
the 3-phase line to the transformer. 

Today that G-E Copper Oxide is the same rectifier. 
The single major change was the division of the unit 
into two parts for your convenience in handling and 

The story will be the same in the future. You can 
buy with confidence now, because changes will be 
few. It was "right" to begin with. That's what counts. 

Write to us now for more information. Section 
A-9433, Appliance and Merchandise Department, 
General Electric Company, Bridgeport, Connecticut. 





Edited by James J. Finn 

Volume 14 


Number 2 

Index and Monthly Chat 


The Language of Lighting .... 


An Analysis of Brush Operation 
on Commutating Equipment 

National Carbon Company 


Projectionist + Serviceman = A 
Star Show Business Team . . 
Leroy Chadbourne 


Try These Canadian License Ex- 

amination Questions 


The Zeiss Ikon Stereoscopic 

Some Television Problems from 

Motion Picture Process .... 


the Motion Picture Stand- 

Z. I. Technical Bureau 



G. L. Beers, E. W. Engstrom 

News Notes 

and I. G. Maloff 

Fifth Subscription Contest Dia- 

Technical Hints 

gram; Many Winners on 

Broadcast Amplifier 


Miscellaneous Items 

Published Monthly by 


Circulation Manager, Ruth Entracht 

Subscription Representatives 

Australia: McGills, 183 Elizabeth St., Melbourne 
New Zealand: Te Aro Book Depot, Ltd., 64 Courtenay Place Wellington 
England and Dominions: Wm. Dawson & Sons, Ltd., Pilgrim St., London, E. C. 4. 

Yearly Subscription: United 
States and possessions, $2 (two 
years, $3) ; Canada and foreign 
countries, $2.50. Single copies, 
25 cents. Changes of address 
should be submitted two weeks 
in advance of publication date to 
insure receipt of current issue. 
Entered as second-class matter 

February 8, 1932, at the Post 
Office at New York, N. Y. under 
the act of March 3, 1879. 
Contents copyrighted 1939 by 
James J. Finn Publishing Corp. 
International Projectionist 
is not responsible for personal 
opinions appearing in signed 
articles in its columns. 

Monthly Chat 

RELIABLE estimates place the num- 
ber of theatres still using low-in- 
tensity projection at about 8,000. Grant- 
ing that this figure is correct, indict- 
ments are in order for both the merchan- 
disers and the ultimate users of the 
Suprex arc. Equipment distributors re- 
port that the cost of two lamps plus 
conversion units represents a sum which 
most small theatres are unable or un- 
wilhng to expend. Exhibitors add still 
another objection, that relating to in- 
creased operating costs for Suprex over 
l.-i. equipment, their contention being 
that the advertised "'few cents per hour" 
extra cost actually may run as high as 
ten cents. This matter of operating 
costs merits examination by some im- 
partial group — and the basis for such 
investigation should be not the minimum 
but the ideal operating conditions. 

Whatever the reason for the failure of 
Suprex to make a deeper dent in the 
exhibition field, it is an industry dis- 
grace that 8,000 theatres catering to the 
largest number of steady moviegoers are 
offering projection the result of which 
is highly unsatisfactory with black-and- 
white prints and positively horrific with 
color prints. 

Incidentally, we notice in our travels 
that many Suprex arcs are being oper- 
ated far above approved ratings. About 
48 amps, for the smaller and about 60 
amps, for the larger trims are the cor- 
rect figures. We've seen these figures 
exceeded by more than 10 amperes — all 
to no purpose other than the waste of 
juice and carbons. 

OUR presentation over the past few 
months of copious data relative to 
the present status of television seems to 
have cooled many a projectionist brow 
that has been highly feverish as a re- 
sult of foreseeing the passing suddenly 
of the motion picture theatre. Not that 
any attempt was, or will be, made to 
minimize the probable unfavorable effect 
of television upon the exhibition field; 
not at all. But the facts as set forth 
herein did serve to dispel in great meas- 
ure the widely-held view that "television 
just around the corner" constituted a 
death warrant for the film exhibition 
field within a very few months. 

That television is a potential formid- 
able competitor for the motion picture 
theatre there can be not the slightest 
doubt (although it seems likely that the 
studios will be busier than ever provid- 
ing network product) ; yet the ex- 
hibition field can do much to improve 
its present position and thereby minim- 
ize the ill effects of television competi- 
tion if it will only take the necessary 

Meanwhile it is again in order to warn 
projectionists against the numerous tele- 
vision "schools" which are sprouting all 
over the country. Those men who know 
their sound-picture stuff should have no 
difficulty in grasping the what, how and 
why of television when the proper time 
arrives. That time assuredly is not yet. 



It is because you can see it better, of course. In 
the stronger light you can see more clearly the 
details of pattern and construction. In daylight 
you see its true color. 

This simple illustration explains the favorable 
reaction of patrons to High Intensity projection, 
now found in more than one third of the theaters 
in this country. This stronger, snow white light 
enables patrons to see all pictures more clearly 


and color features in more accurate hues than is 
possible with low intensity projection. 

Simplified High Intensity projection gives two 
to three times as much light on the projection 
screen as low intensity. Yet it costs so little 
more that one extra admission per show will 
pay the difference. Ask your dealer's salesman 
to show you the book, "Yes — But What Will 
It Cost?" 






The words "National" and "Suprex" are trade-marks of National Carbon Company, In 


"oonQQannnnnnooQaaao anODO ° 


Unit of Union Carbide Him and Carbon Corporation 


General Offices: 30 East 42nd Street, New York, N. Y. 



MR -6 I93S 

©C1B 408305 





An Analysis of Brush Operation 
on Commutating Equipment 


BRUSHES on commutating equip- 
ment have three distinct func- 
tions to perform. First, they 
must carry the load current to and 
from the rotating element of the ma- 
chine, the armature; second, they must 
resist destructive action from the volt- 
age induced in imperfectly compensated 
armature coils undergoing commuta- 
tion; third, they must act as a bearing 
material, preferably without any ap- 
plied lubrication, maintaining contact 
with the commutator at surface speeds 
which may be as high as 70 miles per 

It is difficult to obtain, in one mate- 
rial, the ideal properties for each of 
these divergent functions. It is there- 
fore necessary to seek that combination 
of properties which will give optimum 
performance in all respects. Obviously, 
the combination that is entirely satis- 
factory under one set of conditions 
may prove less satisfactory when con- 
ditions are changed. 

Individual opinions may differ in re- 
spect to what constitutes satisfactory 
brush operation. However, the follow- 

ing can be considered essential ele- 
ments of completely satisfactory opera- 
tion and their attainment, in the fullest 
possible degree, should be sought. 

1. Freedom from injurious spark- 

Negligible commutator wear. 
Uniform gloss over commutator 


4. Minimum electrical and mechani- 
cal losses. 

5. Quietness of operation. 

6. Good brush life. 

Sparking may result from a variety 
of causes. Failure to complete reversal 
of current in the armature coil under- 
going commutation, while short-cir- 
cuited by the brush, is one source of 
sparking. Over-reversal of current is 
another. Too rapid change of current 
in the short-circuited coil, interruption 
of contact between brush and com- 
mutator, disintegration of brush faces, 
breakdown of commutator surface film, 
formation of high-resistance glaze on 
commutator surface, and selective 

action — that is, unequal division of cur- 
rent among the several brushes — are a 
few of the sources of sparking which 
may be encountered at one time or an- 

Commutator wear may result from 
the presence of abrasive particles in the 
brush. Burning of the commutator sur- 
face, due to faulty operation, may also 
be the source of considerable wear. 
Likewise, the reduction in commutator 
life resulting from the necessity for 
frequent resurfacing should be classed 
as commutator wear. With satisfac- 
tory brush operation, commutator wear 
should not be an appreciable item of 
machine depreciation. 

The nature of the commutator sur- 
face has a pronounced influence on 
brush operation, as will be pointed out 
later in this discussion. Satisfactory 
operation requires that a smooth sur- 
face of uniform character be main- 
tained. Change in character of com- 
mutator surface is almost certain to re- 
sult in noticeable effect on brush per- 

Energy losses from short-circuited 


current in the armature coils during 
commutation, from the resistance of a 
glazed commutator surface to the pass- 
age of load current, from the unbal- 
ancing effects of selective action, and 
from the friction of the brushes may 
at times be enough to seriously affect 
the efficiency or the satisfactory per- 


Exaggerated drawing illustrating 

nature of contact between brush 

and commutator 

formance of a motor or generator. 
However, with proper brush selection 
and operation, these losses can be kept 
to a small value. 

Quietness of operation is dependent, 
primarily, on the maintenance of un- 
interrupted contact between brushes 
and commutator. Even where free- 
dom from noise is not an essential 
characteristic of performance, the firm 
contact on which quiet operation de- 
pends has an important influence on 
satisfactory performace in other re- 

Brush life should not be made a 
primary objective in brush application. 
If the other elements of satisfactory 
brush operation are attained, reasonable 
brush life may well be expected; but 
long brush life obtained at the sacrifice 
of performance in some other respect 
may prove far from economical. 

• Nature of Brush Contact 

Before undertaking a discussion of 
the numerous mutually dependent fac- 
tors on which the attainment of satis- 
factory brush operation depends, it 
would be well to consider the nature of 
the contact between a brush and the 

It should be realized that the com- 
mutator and the brush, however highly 
polished they may be, do not necessarily 
present to each other perfectly smooth 
surfaces of identical curvature. Due to 
the play of the brush in its holder, and 
the yielding of supporting members 
under stress, the brush face may have 
a slightly longer radius of curvature 
than the commutator. In such case the 
actual area of solid contact, for a par- 
ticular brush at a given instant is 
probably confined to a relatively short 
span of the brush face in the direc- 
tion of rotation. 

Furthermore, there are indications 

that within this area actual contact be- 
tween brush and commutator is limited 
to a number of points carrying current 
at an extremely high current density. 
Movement of the commutator under the 
brush face, mechanical abrasion and 
the destructive effects of the high local 
current densities cause constant shift- 
ing of these points of contact so that 
solid contact on any single point of 
either commutator or brush face is 
probably of extremely short duration, 
except for firmly imbedded points 
which protrude to a substantial de- 
gree beyond the surrounding surface. 

There are three types of paths 
through which the current flows be- 
tween commutator and brush: the 
points of solid contact, mentioned pre- 
viously; adjacent areas in which free 
particles of carbon, graphite, copper or 
other electrically conducting dust pro- 
vide a conducting path; and open gap, 
across which some current may pass in 
the form of an arc. Fig. 1 illustrates, 
in exaggerated form, this conception 
of brush to commutator contact. 

The assumption that actual contact 
between brush and commuator is 
limited, for a given instant, to only a 
small portion of the brush thickness 
does not justify the further assumption 
that commutation must be effected while 
the mica gap between two commuta- 
tor segments is traveling that short 
distance. Not only do the actual points 
of contact shift rapidly, but the same 
is true of the area within which those 
points lie. 

It is quite possible for contact to oc- 
cur at points scattered over essentially 
the full area of the brush face during 
a single commutation interval. There- 
fore, the fact that a brush shows uni- 
form polish over the entire face does not 
preclude the possibility of contact at 
any given instant having been limited 
to a relatively small portion of the total 
face area. 

When there are several brushes of 
hke polarity, connected in multiple, one 
seems fully justified in considering the 
cycle of commutation to occupy the full 
time required for the mica gap to 
traverse the brush face from leading to 


Commutator surface film 
greatly magnified 

trailing edge. There may be instances 
in which the movement of the area of 
contact during a single commutation in- 
terval fails to cover the full brush thick- 
ness and completion of commutation is 
forced to take place within a very short 
arc of rotation. However, with normal 

performance and good brush and com- 
mutator surfaces, it seems probable that 
such cases are the exception rather than 
the rule. 

There appears to be no necessity, as 
has at times been suggested, of aban- 
doning the classical concept that the 
normal period of short-circuit for a coil 
undergoing commutation extends from 
the leading edge to the trailing edge of 
the brush. 

Inasmuch as firm contact between 
brushes and commutator is essential to 
satisfactory brush performance, protrud- 
ing mica cannot be tolerated. For- 
tunately, the practice of undercutting 
the mica below the surface of the cop- 
per segments has become general. If 
this operation is carefully performed, 
and no fins of mica are left at the sides 
of the slots, brush application is made 
substantially simpler. 

In the following discussion it is as- 
sumed that the mica has been properly 
under-cut and no reference is made to 
complications which would certainly re- 
sult were protruding mica present. It 
is further assumed that the commutator 
has been finished to a smooth surface of 
essentially true cylindrical form, free 
from high or low spots of appreciable 
eccentricity or area. 

• Commutator Surface Film 

One of the most important factors 
affecting brush performance is the sur- 
face film on the commutator. The exact 
nature of the surface film varies greatly 

th operating and atmospheric condi- 
tions, and there is evidence that the 
presence or absence of copper oxides 
in this commutator film may greatly in- 
fluence performance. Graphite is also 
frequently found to be a constituent of 
the surface film. In some cases this may 
be rubbed into the irregularities of the 
commutator surface by the wiping action 
of the brush. In other cases, there are 
indications that the graphite is trans- 
ferred from brush to copper by electro- 
lytic action. 

The brush face and commutator sur- 
face, in highly magnified form, may be 
considered as resembling the sectional 
drawing in Fig. 2. No matter how care- 


fully prepared, or how highly they may 
be polished, a powerful microscope will 
disclose minor irregularities in brush 
and commutator surfaces. 

A raw copper surface on the com- 
mutator does not lend itself to good 
brush performance. Some oxidation of 



Typical Eastman 


EASTMAN Plus-X for general studio work 
. . . Super-XX for all difficult exposures . . . 
Background-X for backgrounds and all- 
round exterior work. . . . All three of these 
new negative films have special features 
suited to their particular fields . . . plus the 
typical Eastman reliability that has served 
the industry so well in the past. Eastman 
Kodak Company, Rochester, N. Y. (J. E. 
Brulatour, Inc., Distributors, Fort Lee, 
Chicago. Hollywood.) 

EASTMAN Plus-X ... 
Super-XX ... Buckground-X 


the surface appears to be advantageous, 
improving commutation and reducing 
friction. It is hard to say just how far 
oxidation can be carried before en- 
countering disturbing effects. Certainly 
it must stop short of actual burning, re- 
sulting in etching or pitting of the sur- 
face of the copper segments. 

The development of an oxide surface 
film in service may require a period of 
several days or even weeks, depending 
on machine and operating conditions and 
the properties of the brushes themselves. 
Some electro-graphitic brushes must be 
operated at a substantial current den- 
sity to result in the formation of the de- 
sired surface film. At low average cur- 
rent density no film is developed by 
such brushes, and film already present 
may break down, exposing spots or 
streaks of raw copper. When this condi- 
tion develops, copper or copper oxide 
particles may deposit in the brush faces 
and threading of the commutator result. 

Threading is the term used to describe 
the development of fine, thread-like 
grooves in the commutator surface. This 
type of film breakdown may account for 
operating difficulties sometimes en- 
countered, under sustained low load con- 
ditions, on machines which have previ- 
ously given good performance when op- 
erating at normal load. The develop- 
ment of oxide film is sometimes accel- 
erated by the application of external 
heat to the commutator. 

It is possible that this phenomenon 
of film breakdown at low average den- 
sity is associated with the high friction 
of some electro-graphitic brush grades 
at low interface temperature and the 
sharp decrease in friction when the in- 
terface temperature rises to a certain 
critical value. Assuming there to be 
such a relationship, it still is difficult 
to say which of these phenomena is 
"cause" and which "effect." The sub- 
ject of temperature effect on coefficient 
of friction has been discussed at length 
by Dr. S. W. Glass. 1 

The property of forming a graphitic 
film on the commutator varies with dif- 
ferent grades of brushes. Some graph- 
itic deposit on the commutator is desir- 
able. It reduces friction, improves inti- 
macy of contact between brush and 
commutator, and probably helps main- 
tain the interface resistance at the value 
necessary for good commutation. It is 
not essential, however, that the amount 
of graphite deposited on the commutator 
by the brush be large. 

Some brushes have a polishing or film 
removing effect on the commutator sur- 
face. Such property is sometimes highly 
beneficial to brush performance. It can 
be imparted to a brush in sufficient de- 
gree to prevent the development of a 
high-resistance film from oil vapor or 

other atmospheric contamination, and 
even to overcome a mild tendency to- 
ward edge burning and bar marking 
from over-oxidation, yet without produc- 
ing sufficient abrasive effect to result in 
noticeable commutator wear. 

The choice between a film forming 
and a polishing, or film removing, grade 
is often a matter of operating and local 
conditions. The same type of machine 
which requires a film forming brush 
when operated at light average load in 
a clean, dry atmosphere may require 
a polishing grade when operated at full 
load in the presence of oil vapor. The 
range and duration of load fluctuations, 
as well as the average load value, may 
have an influence on film formation and 
resulting brush performance. 

• Disturbing Factors 

In the article 1 previously referred to, 
Dr. Glass mentions a number of mate- 
rials which have, an unfavorable influence 
on the commutator surface film. The 
presence or absence of such atmospheric 
contamination, which Dr. Glass terms 
"contact poisons," may be the decid- 
ing factor in determining the type of 
brush which will give best performance. 

Materials having a deoxidizing effect 
disturb brush friction and commutation 
by breaking down the oxide film on the 
commutator. The presence of chlorine 
in the atmosphere is very disturbing to 
brush performance due to its unfavor- 

able influence on the commutator sur- 
face film. Sulphur tends to develop a 
dark, glossy surface on the commutator 
but its effect on performance is gener- 
ally detrimental. The unsatisfactory 
performance encountered in the pres- 
ence of a sulphide or oil film probably 
results from excessively high contact 

Hellmund and Ludwig 2 have shown 
that sparking underneath the brush face 
is liable to occur when the voltage drop 
across the contact path appreciably ex- 
ceeds 3 volts. Therefore, while a drop 
of approximately 1 volt may be needed 
to properly control the voltage in the 
armature coil short-circuited by the 
brush, too high a drop may itself be a 
cause of trouble. 

The same authors point out that a 
very rapid change of current during 
commutation results in much higher 
contact drop than that observed when 
commutation is effected more gradually. 
Faulty interpole adjustment, contact 
over less than the full width of commu- 
tator segments, use of brushes that are 
too thin, or any other condition tending 
to shorten the commutation interval and 
compel over-rapid change of current in 
the commutating coil may produce de- 
structive sparking under the brush face 
(Continued on page 23) 

2 'Sparking Under Brushes of Commutator 
Machines" — R. E. Hellmund and L. R. Ludwig 
— Electrical Engineering, March, 1935. 

Try These Canadian Examination Questions 

^'The Measurement of the Frictional Char- 
acteristics of Brushes" — Dr. S. W. Glass — 
Modern Pyramids, No. 2. 

PROJECTIONISTS generally have 
manifested keen interest in the ex- 
aminations offered periodically by the 
Province of Ontario, Canada, as a re- 
quirement for projectionist licenses of 
the first, second and third classes. 
Therefore, I. P. has decided to pub- 
lish each month a group of questions 
culled from these examinations, the an- 
swers to each group being presented in 
the following issue. 

Generally regarded as constituting 
the most difficult examinations offered 
anywhere, these questions should prove 
particularly helpful to the younger 
craftsmen and at the same time provide 
the so-called old-timers with an oppor- 
tunity to brush up on their knowledge 
of the trade which they have pursued 
for so many years. Examinations for 
first-class licenses comprise 24 ques- 
tions which must be answered within 
three and one-half hours, and are 
divided into five sections relating to 
Projection and Film, Electrical, Me- 
chanism, General and Safety, and 

No written answers to I. P. are 
solicited, and each participant can keep 
his own score on the basis of 100% 
as a maximum and 80% as a minimum 
passing grade, with the value allotted 
being indicated alongside each question. 

The first group of questions from 
the examination for licenses of the 
first class are appended hereto: 

1. (a) Name and describe in de- 
tail three types of condenser lenses, 
and explain how to find the focal 
length of each. (Value 3.) 

(b) Find the equivalent focus of 
a 7.5-inch bi-convex and a 7.5-inch 
meniscus lens. (3.) 

(c) Has an elliptical mirror any 
chromatic aberration? Tell your rea- 
sons for your answer. (3.) 

2. Describe fully three types of 
projection screens and state which in 
vour opinion gives the best results. 

3. Why does the objective lens of 
a projector consist of two bi-convex, a 
plano-concave and a meniscus lens of 
different kinds of glass? (2.) 

4. Using a standard release print: 

(a) Why is the motor-start dis- 
tance to the changeover 12 feet and 
6 frames? (2.) 

(b) Tell how to find out the exact 
motor pick-up speed. (2.) 

5. (a) Name and describe the 
various kinds of 35 mm. film that are 
in use. (1.) 

(b) Where can the various types 
of film be used? (1.) 



Some Television Problems From the 
Motion Picture Standpoint + 



THE prime objective of television, 
in common with other pictorial 
arts, is to create an illusion. There 
are certain limitations on how good the 
illusion can be: some inherent and 
others dependent on the state of the art. 
Many of these limitations have a 
counterpart in motion pictures, and it is 
the purpose of this paper to review and 
compare some of these mutual restric- 

Picture detail in motion pictures is 
ultimately determined by the optical sys- 
tem and the resolution of the film. The 
factors determining picture detail in 
television are more complex. The fre- 
quency-band width limitations imposed 
by a single-channel communication sys- 
tem suitable for television broadcasting 
makes it necessary to divide the scene 
arbitrarily into elemental areas and 
transmit the information representative 
of light and shade, area by area and 
line by line until the entire scene has 
been scanned. 

With such a television system the 
basic factors determining picture detail 
are the number of scanning lines, the 

tj. Soc. Mot. Pict. Eng., XXXII (Feb. 1939). 



Television will undoubtedly utilize mo- 
tion picture film to a great extent for 
the transmission of programs. Some 
of the problems incident to scanning 
the film image, including those relat- 
ing to the use of an intermittent 
projector mechanism, are detailed in 
the appended condensation of this 
extremely interesting paper. 

size of the scanning spot, the frequency- 
band width, and the optical system. In- 
practice the first two factors are 
definitely related, since the size of the 
scanning spot is commensurate with the 
distance between centers of scanning 

In the television standards of the 
Radio Manufacturers Assoc. (R.M.A.) 
scanning is expressed in terms of the 
total number of lines from top to bot- 
tom from the beginning of one frame 
to the beginning of the next frame. 
Since in a practical television system 
both spot size and frequency-band width 
are chosen on the basis of the number 
of scanning lines, the inherent resolution 
of a television system may be expressed 
as the number of scanning lines per 


r v.* t '^ 

-—■■ - ,i- — 


itS^' -Him 






istics repre- 


sentative of 


images for 





»-i-7— "3|pp^ 

of scanning 


^^. -J^ 



frame. Fig. 1 is made up of four repeti- 
tions of the same subject with detail 
equivalent to 60, 120, 180, and 240 
scanning lines. 

Another means for evaluating the reso- 
lution of a television system is to esti- 
mate its ability to tell a desired story 
ill comparison with 16 mm. home movie 
film and equipment. The result of such 
a comparison by a number of observers 
is that a 400- to 500-line television sys- 
tem compares favorably with 16 mm. 
home movies in permitting observers to 
understand and follow the action and 
story. The scanning standard adopted 
by the R.M.A. is 441 scanning lines 
per frame. 

• Frame Frequency, Flicker 

Television images consist of rapidly 
superimposed individual frames much 
the same as in motion pictures. In the 
case of motion pictures a group of time- 
related stills is projected at a uniform 
rate, rapid enough to form a continuous 
picture through persistence of vision. 
By present methods, each frame of a 
television image is built up element by 
element in some definite order and these 
time-related frames are reproduced at 
a rapid rate. 

In motion pictures the frame fre- 
quency determines how well the system 
will reproduce objects in motion. This 
has been standardized at 24 frames per 
second. In television other factors than 
the ability to reproduce motion have 
made it necessary to use a frame fre- 
quency of 30 per second. 

Motion picture projectors commonly 
used are of the intermittent type. The 
usual cycle of such a projector is that 
at the end of each projection period 
the projection light is cut off by a 
shutter, the film is then moved a step 
so that the succeeding frame registers 
with the picture aperture, and the 
shutter then opens, starting the next 
projection period. This is repeated 24 
times per second. 

Since projection at 24 light-pulses 
per second with the screen brightness 
levels used in motion pictures causes 
too great a flicker effect, the light is 
cut off also at the middle of the pro- 
jection period for each frame for a 
time equivalent to the period that it 



is cut off while the film is moved from 
one frame to the next. This results in 
projection at 24 frames per second, 
with 48 equal and equally spaced light- 
pulses. Such an arrangement provides 
satisfactory results from the flicker 

In television, because of the manner 
in which the image is reconstructed, 
a continuous scanning process, it is 
not practicable to break up each light 
pulse further by means of a shutter 
in a manner similar to that used in 
the projection of motion pictures. We 
therefore have in an elementary tele- 
vision system a flicker frequency corre- 
sponding with the actual frame frequency. 
This is satisfactory at very low levels of 
screen brightness, but becomes increas- 
ingly objectionable as the screen bright- 
ness is raised. 

In motion pictures the projector 
shutter opening in terms of degrees 
for each frame has an important effect 
on the flicker characteristics. Cathode- 
ray tubes — Kinescopes — are at present 
the preferred means for television im- 
age reproduction. In the Kinescope 
each element of the image on the 
luminescent screen, when excited by 
the electron beam, fluoresces and as- 
sumes a value of brightness correspond- 
ing with the value of the electron- 
beam strength. Upon removing the 
excitation this brightness then decays 
(phosphoresces) in an exponential 
manner and at a rate dependent upon 
the screen material. 

The phosphorescence or persistence 
of the image screen aids the persist- 
ence of vision of the eye in viewing 
the reproduced image. However, as 
previously stated, far too much flicker 
is present at 24 or 30 frames per sec- 
ond for the desired levels of screen 

• Method of Scanning 

A particular method of scanning is 
therefore used to modify the overall 
image flicker. This is possible because 
scanning is a continuous process. Scan- 
ning may be in equal horizontal strips 
or lines from top to bottom in numer- 
ical order of lines 1, 2, 3, 4, ... . 
(progressive scanning). This results 
in one overall light-pulse for each 
frame. If the procedure is modified 
so that scanning is for the first half 
of one frame period in the order of 
lines 1, 3, 5, 7, 9, . . . ., from top to 
bottom of the frame, and for the sec- 
ond half of the frame period in the 
order of lines, 2, 4, 6, 8, 10, . . . ., 
from top to bottom of the frame (inter- 
laced scanning), then the flicker effect 
of the reproduced image is changed. 
This method of scanning is shown dia- 
gramatically in Fig. 2. 

Each frame now consists of two por- 
tions (two fields) with respect to time: 

each field composed of a group of 
alternate lines, and the two sets of 
alternate lines are properly staggered 
to form a complete interlaced pattern. 
In progressive scanning each line 
flickers once per frame, and neighbor- 
ing lines differ in time relation only 
by the time required for scanning one 
line. There is, therefore, no notice- 
able inter-line effect. In interlaced 
scanning also each line flickers one 
per frame, but neighboring lines dif- 
fer in time relation by one-half a 
frame period. This results in two 
flicker effects— an overall effect and an 
inter-line effect. 

As previously stated, a frame fre- 
quency of 30 per second with pro- 
gressive scanning produces an intoler- 
able flicker. A frame frequency of 60 
per second is certainly satisfactory from 
the flicker standpoint, but the fre- 
quency-band width required for trans- 
mission is doubled. With interlaced 
scanning at 30 frames, the overall 
flicker effect is the same as with 60 
frames progressive scanning, and no 
increase in frequency-band width is 
required. Each line flickers at the rate 
of 30 per second and adjacent lines 
flicker with respect to each other, since 
they are scanned with a time-difference 
of 1/60 of a second. At optimum view- 
ing distances for television images and 
for practicable levels of screen bright- 
ness this inter-line flicker is not notice- 

A frame-frequency effect peculiar to 
television is encountered in the opera- 
tion of cathode-ray television receivers 
from an alternating-current power-sup- 
ply system. The effects of ripple volt- 
ages and fields appear in the repro- 
duced image in a variety of forms and 
from numerous sources. If the frame- 
frequency differs from the power-supply 
frequency, that is, differs except in 
terms of integral multiples or sub- 
multiples, then these effects move 
across the image at rates dependent 
upon the time-difference between the 
frame-frequency (multiple) and the 
power-supply frequency. This moving 
ripple pattern' is almost as disturbing 
as flicker and the visual effects are 
about th§ "same. 

Also, for interlaced scanning these 


Diagrammatic illustration 

of progressive scanning 

and interlaced scanning 


supply frequency, 30 frames for a 60- 
cycle source, then the effects are sta- 
tionary on the image and very much 
less pronounced, thus making it pos- 
sible to obtain satisfactory performance 
when using comparatively inexpensive 

On the basis of these factors the 
R.M.A. has standardized interlaced 
scanning with a frame-frequency of 30 
per second and a field-frequency of 60 
per second. 

• Film Projection Process 

Motion picture film is one source of 
program material for television. With 
electronic scanning methods it is usual 
to project an image of the film mov- 
ing or stationary on to some element 
of the electronic translating device. 
This may be accomplished by the use 
of an intermittent type of projector, a 
continuous projector having an optical 
intermittent, or a system in which the 
film moves continuously with a com- 
pensating motion of film-image and 
scanning. The particular method used 
is partly determined by the type of 
electronic scanning device. The use 
of 24-frame motion picture film to pro- 
duce 30-frame television with inter- 
laced scanning presents certain special 

In using an Iconoscope as the elec- 
tronic translating device it has been 
customary to use an intermittent type 
of projector. By utilizing the storage 
properties of an Iconoscope, the film- 
image may be projected on to the 
photosensitive mosaic during the time 
between the completion of one field 
scanning and the beginning of the 
next. Scanning then may take place 
and electrical signals may be obtained 
from the mosaic while it is dark. Since 
the field scanning-frequency is at the 
rate of 60 per second, this means a 
short period of projection 60 times a 
second and of a duration of approxi- 
mately 1/800 second. 

With 60 projections per second we 
may hold one frame for three pro- 
jection periods — 3/60 second; the next 
for two projection periods — 2/60 sec- 
ond; the next for three projection 
periods — 3/60 second; the next for 
two projection periods . . . Thus by a 
3:2 ratio of pull-down periods in an 


ripple effects cause moving displace- 
ments in the position of alternate sets 
of lines and tend to destroy the inter- 
laced pattern. If the frame-frequency 
has an integral ratio to the power- 

intermittent and by the use of a shutter 
that is open only during the vertical 
return of the scanning, we may derive 
program material for a 30-frame tele- 
vision system from standard 24-frame 



sound motion picture film, retaining the 
standard film speed. This 3:2 ratio 
of pull-down periods is shown in 
Fig. 3. 

In picture-detail capabilities a 441- 
line television system compares favor- 
ably with 16-mm. home movies. If mo- 
tion picture film is used to provide 
television program material, satisfactory 
results may be expected from 35-mm. 
film; a slight loss in picture-detail will 
result from the use of 16-mm. film, and 
the resolution capabilities of a high- 
definition television system will not be 
utilized if 8-mm. film is used. 

In motion picture work studio light- 
ing and make-up technic are dependent 
upon the color-response characteristics 
of the film. In television the spectral 
response characteristic of the Icono- 
scope controls these factors. The 
Iconoscope gives maximum sensitivity 
in the blue end of the spectrum. The 
most desirable Iconoscope spectral char- 
acteristic for a given application is 
dependent upon the light-source used 
to illuminate the scene. An Iconoscope 
tends to compensate for the high red 
output of the incandescent lamps used 
in studio lighting. 

• Kinescope Characteristics 

For outdoor pick-up work a charac- 
teristic more nearly approximating that 
of panchromatic film is desired. The 
spectral characteristic of the Icono- 
scope can be varied to a considerable 
extent by the sensitization procedure 
employed. Various spectral-response 
characteristics obtained in experimental 
Iconoscopes have indicated that char- 
acteristics can be provided that are 
comparable to those of panchromatic 
and other films. 

The high-intensity arc commonly 
used as a light-source for motion pic- 



Tivo special 
film pro- 

many serious limitations were present 
that the green color of the image re- 
produced on a willemite screen was 
not considered to be particularly un- 
desirable. As television development 
progressed and picture-detail and screen 
brightness improved, the green color 
of the reproduced image became more 
objectionable, and development work 
on luminescent materials to produce 
a black-and-white image was started. 

Kinescopes having luminescent screens 
giving black-and-white pictures of ade- 
quate brilliance are now a commercial 
reality. Individual opinions vary 
greatly as to which is the best white 
for television screens, since the appar- 
ent whiteness of a television image is 
influenced by such factors as the image 
brightness and the background lighting 
in the room in which the image is 
viewed. One thing is certain, and 
that is that purchasers of television 
receivers will demand substantially 
black-and-white images. 

Although the brightness range in 
television images may be limited in 
several portions of the system, the 


Diagram illustrating the 
3:2 ratio of pull-down 
periods in a special 
television film projector 



ture projectors produces an image that present practicable limit is in the 

has satisfactory black-and-white char- Kinescope. The bulb shape of the 

acteristics. In the initial stages of Kinescope is determined by the physi- 

cathode-ray television development so cal characteristics necessary to with- 

stand atmospheric pressure. For this 
reason the screen of a conventional 
Kinescope has a certain curvature, thus 
permitting illuminated parts to throw 
light directly on non-illuminated parts. 
Reflections may occur also from other 
portions of the inner surface of the 

In addition to these reflections, a 
certain amount of light is totally re- 
flected from the glass-air boundary and 
introduces a reduction of range in de- 
tails by halation. These effects have 
been reduced by blackening the inside 
walls of the bulb and by introducing 
a small amount of light-absorbing mate- 
rial in the glass wall. Conventional 
Kinescopes have an available range of 
(Continued on page 24) 


Theatrical television was introduced in 
London, England, with the BBC telecast- 
ing programs recently to the Tatler Thea- 
tre and the Marble Arch Pavilion. Both 
theatres are fully equipped with the most 
advanced Baird projectors and will throw 
the televised programs on a screen 15 by 
12 feet. 

Meanwhile, official BBC figures for 1938 
disclose that over 18 per cent of the total 
program time occupied by television was 
devoted to pix. This represents 172 hours 
out of a 957 total. 


Despite the withdrawal of several 20th 
Century-Fox stars from radio engagements 
and rapidly mounting protests from ex- 
hibitor organizations against radio com- 
petition, the major film companies indicated 
that they will make no move to follow 
the lead of 20th but, on the contrary, en- 
courage radio appearances by their players. 
Radio executives continue to hold that the 
airwaves do not seriously affect the box 
office take on "good" pictures, but in fact 
help it. To all of which exhibitors vote 
an emphatic "No!" 

Just a penny postcard bearing your 
old and new addresses is needed to in- 
sure regular receipt of I. P. You'll like 
this, and we'll appreciate it. Thanks. 




eovW " 



Fifth Subscription Contest Diagram; 
Many Winners on Broadcast Circuit 

OUR tart remarks last month about 
the poor showing made by the craft 
on these Contest diagrams were sent 
■winging back into our bridgework when 
no less than 28 contestants popped up 
with the right answers — the highest 
number of winning entries since the 
Contest was launched. Of course, we 
wish we could ascribe this fine showing 
to a wider participation in the Contest 
or to our editorial prodding, but, alas, 
we fear that the reason therefor lies in 
the great similarity in successive dia- 
grams and in the changes made. 

The current Contest offering (Fig. 1) 

should prove considerably more difficult 
because it applies to an equipment that 
is about five years old, is little used in 
the theatre field, and demands that the 
contestant know his circuits. Some new 
wrinkles in the way of elisions and addi- 
tions have been introduced, but these 
shouldn't impose undue strain on com- 
petent craftsmen. Naturally, practically 
the entire circuit has been redrawn, 
thus it is useless to seize upon faulty 
tracing as a clue to the changes made. 
In toughening up this month's entry 
I. P. is merely following the suggestion 
of a majority of contestants. Ex- 

pressions of opinion as to the desir- 
ability of tracing these diagrams out in 
detail, instead of merely citing the 
changes made therein, are solicited. 

In line with established custom, only 
subscribers to I. P. are eligible to com- 
pete in this Contest. All answers must 
reach I. P. not later than March 21. It 
is not necessary to enclose a copy of 
the diagram; merely list the corrections. 
Each successful contestant will receive a 
one year's free subscription to I. P. 
How many would prefer that the award 
be $1 instead of a subscription? 

A couple contestants failed to score 
this month for what were obviously 
errors in transcribing their answers. 
All answers should be checked carefully 
before mailing to provide against such 
errors — such as substituting "R2" for 
"R12", and the like. 

Last month's circuit was another 
W. E. voice amplifier used for broadcast 
work (Fig. 2). The errors therein 
were : 

1. Dot removed from the crossing at 
the left of R5. 

2. Dot removed from the first cross- 
ing below C2. 

3. Dot added to the crossing at the 
bottom of CI. 

4. Dot added to the crossing at the 
left of R12. 

5. Jumper added between R6 and 

6. Jumper added from terminal 15 
to the first line to the left. 

• 28 Winners on Last Circuit 

The winners on this diagram were: 
Walter Fink, Mahanoy City, Penna. ; 
Lloyd Frazier, Boone, Iowa; M. J. 
Haskin, Detroit, Mich.; Fred Snodgrass, 
New Martinsville, W. Va.; Ralph W. 
Rushworth, Baltimore, Md. ; Calvin E. 
(Foot of Col. 1, next page) 





//O k AC 



The Language of Lighting 

COLOR is a pleasing visual experi- 
ence which nature has used ex- 
tensively to give variety and beauty 
to the landscape and the sky overhead. 
The brilliance of the flowers, the green 
of the trees, the radiance of the sunset, 
and the multicolors in the rainbow, all 
present a kaleidoscope to stimulate in- 
terest in color and to excite human 
ingenuity to duplicate it artificially, that 
this visual experience may be brought 
under man's control and applied where- 
ever desired, day or night, independent 
of nature. To achieve this, in so far 
as it is possible to do so with light, 
one must, of course, know something 
of the theory of color. 

It is necessary, first of all, to become 
familiar with some of the fundamentals 
of color terminology. A color is char- 
acterized by three qualities — hue, bril- 
liance and saturation. 

• Color Terminology 

Hue. It has already been shown that 
hue, the fundamental quality of all 
colors, is determined by the frequency 
of the ether vibrations; thus hue is de- 
termined by the position in the spectrum 
and is identified as red, blue, etc. 

Brilliance. A color of a certain hue 
may be dark or light. This has nothing 
to do with the frequency of the ether 
vibrations, but depends on the amount 
of light reaching the retina of the eye 
in a given time. This characteristic of 
a color which causes it to appear as 
dark or light is known as its brilliance, 
luminosity or brightness. 


Mervine, Pottsville, Penna.; Victor 
Schulman, Brooklyn, N. Y.; George W. 
Finch, Cuyahoga Falls, Ohio; James A. 
Day, Detroit, Mich. 

Also, Lewis M. Edwards, Trenton, 
N. J.; Lewis H. Sigworth, Erie, Penna.; 
Stanley Henry, Beaver City, Nebr.; 
Walter W. Wehr, Allentown, Penna.; 
C. H. Perry, Sudbury, Canada; Vernon 
J. Malstron, Salt Lake City, Utah; Ray 
Mowery, Mahanoy City, Penna.; Ches- 
ter A. Ellison, Reading, Mass.; Francis 
L. Hill, St. Petersburg, Fla.; Hugo 
Bryant, Conway, Ark. 

Also, Geo. Wilde, Columbia, 111.; 
George H. Smith, Weiser. Idaho; James 
C. Walker, Phillipsburg, N. J.; Howard 
B. Smith, Springfield, Mass.; Kenneth 
McLay, Milwaukee, Wis.; Raymond A. 
Wood, Poughkeepsie, N. Y.; Joseph J. 
Korzak, Grand Rapids, Mich.; J. J. 
Edgerly, Fall River, Mass.; and Ralph 
M. Hinshaw, Weiser, Idaho. 

//. COLOR 

Saturation. If to a color of one wave- 
length — red, for example — white light 
consisting of all visible wave-lengths is 
gradually added, the red becomes paler 
and paler. In its original condition, this 
red is regarded as a pure color and is 
said to be perfectly saturated. It be- 
comes less and less saturated as the 
white light is added. 

Almost all colors seen in ordinary 
life are due to selective reflection of 
white light, and since some portion of 
all the wave-lengths is reflected, these 
colors are usually far from saturated. 
When a leaf is seen by sunlight, for 
example, it appears green because the 
leaf reflects the green wave-lengths more 
efficiently than any of the others. How- 
ever, it does not completely absorb all 
other wave-lengths; nor does it reflect 
all the green. 

It should be emphasized at this time 
that a color is by no means a simple 
elementary phenomenon, but a complex 
psychological state, depending not only 
on whether the stimulating ether vibra- 
tions are long or short, or the level of 
the light high or low, but on many 
other factors as well. Among these 
might be mentioned the condition of the 
retina with respect to its previous stimu- 
lation (state of adapation) ; the stimu- 
lation taking place in neighboring por- 
tions of the retina (contrast) ; the part 
of the retina being affected by the light, 
and the duration of the stimulus. 

These factors combine to give rise 
to an almost endless variety of colors, 
equalled only by the variety of names 
which fashion experts, and others, find 

to attach to them. It is instructive to 
observe that, in spite of all these com- 
plications, visual sensations are of such 

Color mixture by addition of wave- 
lengths of light 

Color mixture by subtraction of wave- 
lengths of light 

a nature that all colors, including white, 
can be produced by combining three 
properly selected primary colors accord- 
ing to certain laws of color mixing. 

• Color Mixing Methods 

There are two methods of color mix- 
ing, the additive and subtr active. If on 
a screen a blue beam and a separate 
yellow beam of light are projected, the 
portion where they overlap will be 
white. These colors are, therefore, said 
to be complementary, and this method 
of combining colored beams is called 
the additive method of color mixing. The 
tendency in this method is always to 
produce more light and to approach 
white. The primary colors for the addi- 
tive method are red, green, and blue. 
Red and green combine to give yellow 
and all the intermediate shades; red and 
blue give magenta, and green and blue 
give a blue-green. This method of color- 
mixing is illustrated in Fig. 1. 

If a beam of white light is made to 
pass through a piece of yellow glass 
and a piece of blue-green glass placed 
behind one another, the light passing 
through will be seen as green. This is 
called subtractive color mixing and the 
tendency in such cases is to obtain less 
light and to approach black. The three 
primaries for subtractive mixture are the 
exact complements of those for the addi- 
tive method. These are blue-green, 
magenta, and yellow (Fig. 2). They are 
approximately the blue, red, and yellow 
which are used in painting. Colored 
pigments, when mixed, behave accord- 
(Continued on page 21) 



Projectionist -)- Serviceman — A 
Star Show Business Team 

Altec Service Corp. Files Reveal how Cooperative Effort Keeps the Show Going 

OFTEN as I watched the sound sys- 
tem serviceman busy himself in 
my projection room I have been 
struck by the thought that here indeed 
was a novel form of teamwork — between 
projectionist and serviceman — concern- 
ing which there had been very little of 
interest said or written. And, more im- 
portant, such teamwork was not dedi- 
cated to the glory of dear old Siwash but 
rather to the very practical proposition 
of helping mightily in keeping a great 
industry going. 

The more I speculated on this team- 
work within the confines of a projection 
room, without benefit of applauding 
crowds or blaring bands, the more con- 
vinced I became that here was a story 
clamoring to be told. 

So one day I hied myself over to the 
offices of Altec Service Corp., cornered 
some of the boys and persuaded them 
to dig out of their files some typical 
instances — "real life stories," you might 
term them — of how the team of projec- 
tionist plus serviceman could lick a prob- 
lem in the heartiest kind of cooperation, 
when neither of them could lick it alone 
half as easily. In other words, it was 
"teamplays" I was looking for; and here 
are the stories — out of dozens of such 
experiences — the Altec men dug up for 

• Fast-Thinking Projectionist 

The Altec inspector received an emer- 
gency call from the Jefferson Theatre, 
Newport News, Va. The theatre advised 
that the stage speakers had failed, and 
would the Altec men come at once? 
When the latter arrived, he found the 
stage speakers completely out — and was 
astounded to find that the show was still 
going on to the satisfaction of a good- 
natured audience, all as a result of some 
fast thinking on the part of the projec- 

When the sound from the stage speak- 
ers failed, and while the serviceman was 
enroute, the projectionist didn't sit back 
and twiddle his thumbs. Instead, he 
moved the monitor horn from its usual 
location and placed it at a room port- 
hole into the auditorium. He was deliver- 
ing sound to the audience — not from the 
stage but from the back of the house! 
Unorthodox procedure though that was, 
it kept the show going — and prevented 

This was the first time that Altec's 
monthly trouble call analyses ever re- 


corded this ingenious method by which 
a projectionist who was "on his toes" 
literally forced the show over. 

Whether engineering training or plain 
hard experience is the more important 
asset in sound system trouble-shooting 
is one of those arguments for the long 
winter evenings. Engineering training 
provides a background which allows the 
trouble shooter to think out the relation 
between trouble-cause and trouble-ej^ect. 
That method often takes time. Experi- 
ence, on the other hand, gives the 
trouble-shooter that uncanny ability to 
"put the finger", almost by instinct on 
the parts which are causing the trouble. 
Call it a "sixth sense" if you like, but 
that kind of experience can be gained 
only after a man has handled literally 
hundreds of emergency calls. 

• Hot and Cold Speakers 

The ideal combination, however, is en- 
gineering plus experience — and here's a 
case in point. 

The Palace Theatre, Minneapolis, 
turned in an emergency call for the 
Altec inspector, reporting that the meter 
on the KS-6540 horn current control 

Victor Welman of Cleveland L. V. 160 
caught by a sneak-shot as he prepares 
to startle the scientific world with his 
contribution to the last SMPE conven- 
tion papers program 

(One Sperber, alleged photographer, also 
sneaked the shot into this slot.) 

cabinet was reading 1.9 amperes in- 
stead of the normal 3 amperes. There 
was no other evidence of trouble, the 
sound reproduction apparently continu- 
ing as normal. 

However, the projectionist had his eyes 
open, and when he noticed that a meter 
was reading abnormally low, he rightly 
took this as a danger signal and called 
the serviceman. 

Upon his arrival, the Altec man im- 
mediately went backstage to check the 
speakers, because he knew that the con- 
trol cabinet furnished the current for 
operating the speaker fields. Then, in- 
stead of staging a big act by taking out 
an assortment of meters to make things 
look "scientific", he just walked up to 
each of the No. 555 receivers, the speak- 
ers, and felt them with his hand to see 
whether they were warm, or cold! 

Experience had taught him that nor- 
mally-operating receivers are slightly 
warm, as a result of the heat dissipated 
in the resistance of the field coil. In 
this case he found that two of the four 
receivers were cold, and this instantly 
gave him the clue for the abnormal cur- 
rent reading on the meter of the KS- 
6540 control cabinet noticed by the pro- 
jectionist. The sound reproduction had 
continued because the remaining two re- 
ceivers were still operating. 

Tracing further, the inspector found 
that the two cold receivers were not op- 
erating because of corroded terminals 
in a horn cable plug. .This caused an 
open circuit which shut off the current 
to these two units. 

• The Villianons Vaudevillian 

Over a period of several months, emer- 
gency calls came in from various thea- 
tres in Texas. The projectionists were 
mystified, and so were the Altec inspect- 
ors when they got to the theatres and 
found that the former had their equip- 
ments in apple pie order. Nothing was 
wrong — except that the No. 555 receiv- 
ers suddenly failed to operate. 

What's more, every theatre in this 
group had exactly the same trouble, for 
no assignable reason. 

The Altec men and the projectionists 
donned their combined thinking caps. 
There was a vaudeville act touring the 
State. After these mysterious failures 



had been piling up on the emergency 
reports, it developed that the failure of 
the horns occurred directly following 
this particular act — in every theatre 

Very mystifying, all this. Then came 
the denouement. It developed that during 
the act in question one of the actors fires 
a blank pistol shot, and the fellow he 
was supposed to shoot always stood right 
in front of the mouth of one of the big 
horns used behind the screen in the 
sound system. 

The concussion from the pistol shot, 
directed into the horn mouth, caused the 
receivers to fail! In each case, either 
the voice coils were found torn entirely 
loose from the receiver diaphragms, or 
the diaphragms themselves were punc- 
tured. The sound entering the large 
horn mouth was carried through the 
narrowing sound passage of the horn 
until it reached the receiver diaphragm 
tiemendously concentrated. 

A friendly word of advice to the vil- 
lian — the vaudevillian, that is — was suffi- 
cient to bring a stop to this wave of 
receiver failures. 

• Lights Burned Brightly 

Many serious shutdowns resulting 
from sound system failure are averted 
by emergency methods which have been 
devised beforehand for just such occa- 
sions. These schemes normally consist 
of cutting out certain parts of the appar- 
atus which, although contributing ma- 
terially to the quality of the sound re- ■ 
production, can be dispensed with in 
an emergency. 

For example, cutting out the final 
power amplifier of the system, and op- 
erating at the reduced power output of 
the preceding amplifier. For example, 
cutting out the pre-amplifier of one ma- 
chine and continuing operation by 
strapping the photo-electric cell from 
the defective machine over to the pre- 
amplifier of the remaining good ma- 
chine. For example, operating the 
exciter lamps on a. c. or storage batter- 
ies in case the d. c. rectifier fails. 

In the case of the Grand Theatre, 
Orlando, Fla., the amplifier failed. The 
projectionist immediately got on the job 
and established the fact that the trouble 
was due to a short-circuited filter con- 
denser. When he determined this, he 
knew just what to do. He opened a 
pre-arranged connection which discon- 
nected this particular filter condenser, 
following which the amplifier was able 
to continue operation on the remaining 
filter condensers. 

Having gotten the show back on the 
sheet, the projectionist called the Altec 
man and told him exactly what had 
happened. The latter, after the show, 
isolated and replaced the particular de- 
fective condenser which caused the 

Somebody in the theatre reported that 
all of the lights in the house had burned 
very brightly for a few minutes on the 
day preceding the condenser failure. 
Using this clue, investigation led to the 
conclusion that the condenser failure had 
resulted from a violent fluctuation in the 

power supply to the theatre. 

Well, the foregoing citations give you 
an idea of what good teamwork between 
projectionist and service inspector can 
do. There are dozens of cases in the 
same files from which these came. Want 
to read more of them? 

Newburgh, N. Y., 2-Men Shift 
Law Wins in High Court 

The long-disputed Newburgh, N. Y., 
ordinance governing the employment of 
projectionists has been unanimously up- 
held by the N. Y. State Court of Ap- 
peals in a final decision on a case of 
great importance to the organized craft 
throughout the country, in view of the 
prestige of the N. Y. Appeals body. 
Adopted originally in 1936, the ordi- 
nance provides for the employment of 
two-men shifts at all times while a thea- 
tre is operating and for licensing by a 
local board of examiners. 

Theatre ,owners contended that the 
ordinance was unconstitutional, that two- 
men shifts are unnecessary, that the law 
was passed through "undue influence" 
(the president of the I. A. Local is also 
Mayor of Newburgh) , and that license 
renewal is permitted without re-examina- 
tion. Opposing counsel stressed the 
safety feature of a full projection crew, 
denied allegations of irregularity in the 
passage of the law, and maintained that 
State law does not prohibit a third-class 
city (as is Newburgh) from making its 
own regulations as long as they don't 
conflict with State law. 

The decision being unanimous, no 
further appeal is likely. 

Large chain theatres in Iowa already 
comply with bill's provisions. The West 
Virginia bill provides in part: 

"While operating such moving pic- 
ture machines each operator shall de- 
vote his entire time to the operation of 
said machines; he shall not leave the 
operating side of such while in use, nor 
engage in any unnecessary conversation 
with anyone, nor perform any other 
duties other than the operation of such 

The bill also provides a penalty of 
$25 a day for non-observance of law, 
with each day constituting a separate 

Nebraska projectionists are seeking 
favorable action on legislation requiring 
toilet facilities in the projection rooms 
of all theatres located in towns of 1,000 
or more population. 


Scores of letters have been received 
anent the decision of the Oklahoma 
Supreme Court which classified motion 
picture projection as a "non-hazardous" 
occupation under the meeting of that 
State's compensation law. but I. P. fails 
to note any concerted action by the craft 
or any section of it looking toward pos- 
sible revision of such laws in Oklahoma 
and elsewhere. 

Ask for Safety Crews in W. Va., 

Iowa ; Nebraska Foray 

Two-men-shift bills have been intro- 
duced in the legislatures of West Vir- 
ginia and of Iowa. Both the I. A. men 
and the exhibitors in latter State pro- 
fessed to know nothing anent source of 
the bill, similar legislation having been 
defeated twice within past four years. 


Jack Durst is now acting as factory 
representative on the Coast for Interna- 
tional Projector Corp. Active in the sound 
picture field since 1928 and identified with 
the development of the Simplex sound sys- 
tem, Durst will contact the Academy and 
other groups in carrying through to re- 
producing equipment design the latest 
production refinements. 

The new streamlined RCA Photophone projector soundhead 

FEBBU AB Y 193 9 


The Zeiss Ikon Stereoscopic Process 


TECHNICAL efforts no less than 
artistic considerations continually 
revive the question as to the possi- 
bilities of perfecting the film picture of 
the present day. Action, speech, music, 
and even color are embodied in the film. 
There is only only thing which it lacks, 
and that is the visual impression of 
three-dimensional solidity in space. 

In the motion picture we see photo- 
graphs, in which the impression of a 
certain degree of substantiality in space 
is simulated through skillful gradation 
in the lighting effects, but the impression 
of true material substance as presented 
by all bodies as we see them in Nature 
is still wholly absent in the modern 
film. Nevertheless, the production of 
pictures conveying the impression of 
solidity in space is an old established 
achievement in the form of stereoscopic 

In the device in which this is accom- 
plished two photographic pictures of an 
object or a person are taken in the place 
of the usual single picture. These two 
pictures are not identical but conform 
to the two pictures as seen respectively 
by the right and the left eye. The pic- 
ture seen with the left eye will show 
the object in question a little more from 
the left, and that seen with the right 
eye a little more from the right. 

When these two pictures are viewed 
jointly in such a way that either eye 
sees only the picture relating to it, the 
impressions imparted through the two 
eyes separately are merged into a single 
picture by our brain with the result that 
we see the represented objects in solid 
relief as we do when viewing them di- 
rectly. In fact, it is only by the joint 
effect of the pictures received and inter- 
preted by the two eyes that we receive 
the natural impression that an object is 
actually occupying a definite position 
in space. 

• Stereo Film Drawbacks 

The reader may remember that be- 
fore the days of the motion picture film 
stereoscopic pictures of this kind were 
frequently shown to the public in the 
so-called panoramic theatres. Even in 
our days photographs are extensively 
taken by amateurs with the aid of stereo- 
scopic cameras and viewed through 
stereoscopes. The disadvantages of this 
method is that the picture can only be 
looked at by only one person at a time. 

For years efforts were made, with 

The accompanying article details the 
latest development in Europe in the 
unceasing quest for commercially prac- 
ticable three-dimensional motion pic- 
tures. This Zeiss Ikon process reveals 
nothing startling new, (including the 
use of polarized light) other than the 
methods of taking and showing the 
pictures, which procedures require 
special attachments for both camera 
and projector. 

varying success, to devise a means of 
showing to a gathering of spectators 
moving pictures of this kind. We may 
mention in this connection the green- 
and-red motion picture shows, in which 
the two component pictures — one red, 
the other green — were projected upon a 
screen. When these pictures were 
viewed through spectacles containing a 
green and red glass or filter, either eya 
would see only the picture appropriate 
to it. 

This method has great drawbacks: 
first, because the color has a very dis- 
turbing " effect, and secondly, because 
many persons do not see colors normally 
or are even color-blind. Moreover, it is 
obvious that color films could never be 
shown stereoscopically by this method. 

Recently a process, on the develop- 
ment of which we (Zeiss Ikon) have 
worked for some considerable time, has 
been tried out with complete success 
on a fairly extensive scale. A stereo- 
scopic film shown in the Ufa-Palast am 
Zoo in Berlin made a sensational im- 
pression upon the 2,000 spectators pres- 
ent on that occasion. This system is based 
upon the use of so-called polarized light. 
Light, it should be recalled, is an electro- 
magnetic mode of wave-motion in which 
normally the oscillations occur in all 
directions at right angles to the line of 
propagation. By the use of special 

A Z. I. stereoscopic film 

filters it is practicable to influence these 
oscillations of light in such a way as to 
confine them to a single definitely de- 
termined plane. 

In the stereoscopic film system de- 
veloped by us the two component pic- 
tures corresponding to the normal dis- 
tance between the human eyes are taken 
within the conventional film picture size 
of the standard film by means of a spe- 
cial optical device forming part of the 
motion camera. As the subdivision of 
the film picture into two halves would 
result in the formation of vertically 
oblong pictures, the associated pairs of 
pictures are taken on the film at right 
angles to their usual position (Fig. 1) 
in order that on the motion picture 
screen they may be restored to the 
normal transverse oblong. 
# Projector Attachment 

In the reproduction on the screen the 
two component pictures are projected 
by means of a special optical attach- 
ment, which can be appended without, 
trouble to any standard motion picture 
projector. In the act of projection the 
pictures are turned through 90° into 
their original position in the standard 
film and rendered coincident on the 
screen. Each of the two beams of rays 
has a polarizing filter included in its 
path in such a way as to impart to the 
two rays a definite form of oscillation 
differing one from the other. The screen 
receives accordingly two rays of light 
which are polarized in different direc- 

An essential requirement of this sys- 
tem is that no element should be allowed 
to intervene which might interfere with 
the polarizing effect at the points where 
the rays of light meet the screen. They 
should accordingly be projected upon a 
screen which ensures the maintenance 
of the particular oscillation imparted to 
the light. Apart from ground glass sur- 
faces, metal surfaces of the nature of 
silver screens are particularly well 
adapted for this purpose. 

If now the two component images be 
viewed through spectacles containing 
likewise two polarizing filters having 
their planes of polarization appropriately 
directed with respect to each another, 
either eye will see only the picture 
appertaining to it, while the rays of 
light proceeding from the other picture 
are extinguished by the filter so far 
as this eye is concerned. The like, 



though reverse, process applies to the 
other eye. The resulting effect is ac- 
cordingly that either eye sees only the 
picture appropriate to it. 

To render this more easily intelligible, 
the entire act of projection is indicated 
diagrammatically in Fig. 2. The film 
contains the two component pictures 
which are merged into one on the pic- 
ture screen through objective and spe- 
cial prisms. At the same time the 
beams of rays corresponding to pictures 
1 and 2 pass each through a polarizing 
filter. The spectator will view these pic- 
tures through spectacles having two 
corresponding polarizing filters. The 
beam of light I appertaining to picture 
1 is allowed to pass through the spectacle 
glass 1, while beam II is extinguished. 
The beam proceeding from picture 2 
passes through the spectacle glass 2, 
while beam I proceeding from picture 
1 is extinguished in this spectacle filter. 

Either eye will therefore see only that 
picture which appertains to it. The 
brain restores the fusion of the two pic- 
tures into one, so that objects and per- 
sons are seen as they appear in nature. 
We now come to the question as to what 
is needed in order to render a projector 
of standard type available for project- 
ing stereo pictures. These requirements 
comprise : 

1. As to the projector: 

(a) An optical front attachment 
for the projection of the component 
pictures by means of the polarizing 

(b) A source of light of high in- 

2. As to the picture screen: 
Metallized linen. 

3. Spectacles with polarizing filters. 

• Screen, Spectacles 

As already described, the stereo front 
attachment with the incorporated prisms 
serves for the projection of the com- 
ponent pictures upon the screen in their 
correct position. This attachment can 
be appended to any standard projector. 
This stereo attachment contains, in addi- 
tion, the two polarizing filters. The 
losses of light which are inseparable 

from the presence of the prisms, the 
polarizing filters, and the spectacles 
worn by the spectator must be made up 
by the use of lamps of increased power. 

To some extent this loss of light is 
made good by the use of a silver screen 
because of its well known much higher 
reflecting capacity. This silver screen, 
as already mentioned, is needed for an- 
other reason. The polarized light is 
required to retain its state of polariza- 
tion. This implies that reflection should 
take place at a metallic surface. An 
ordinary screen would have what is called 
a depolarizing effect, that is to say, it 
would cause the light again to oscillate 
in all directions. Since picture screens 
of the normal type have as a rule a 
restricted angle of dispersion, spectators 
occupying side seals do not see the pic- 
ture in its full brightness. Screens are, 
however, in course of preparation which 
will have a large angle of dispersion, 
that is to say, which will reflect the light 
fairly evenly in all directions. 

Now, as regards the spectacles: The 
older procedures, in which likewise use 
was made of spectacles, did not obtain 
a permanent hold, but this was not by 
reason of the use of spectacles but rather 
because the colored filters used were 
very liable to subject the spectators to 
color flicker. In the case of the new 
polarizing filter spectacles this does not 
arise. Spectacles as such are not re- 
sponsible for failure of the further de- 
velopment of the older attempts. The 
fault lay in the nature of the spectacles. 

It may be regarded as a detracting 
feature of the stereoscopic motion pic- 
ture that spectators are required to put 
on spectacles in order to see it. When, 
however, it is considered that in these 
days everyone is ready to wear protec- 
tive spectacles in glaring sunlight, the 
incidental use of spectacles should not 
be looked upon as a serious obstacle to 
the success of the stereoscopic picture. 
As it happens, the requisite spectacles 
are now made at a very moderate cost. 
It is naturally difficult to say whether 
the stereoscopic film will secure a foot- 
hold in the motion picture theatre, espe- 
cially in film plays. It may, however, 
be regarded as certain that it has great 

Film Component Polarising Filter 

Silver Screen 


Path of the rays in 
the projected light 

possibilities in the service of advertis- 
ing and educational presentations. 

The exhibition of a stereoscopic ad- 
vertising film with ihe Zeiss Ikon equip- 
ment, as referred to, has certainly dem- 
onstrated that the public follows such a 
film with enthusiastic interest, showing 
that it is competent to rivet public at- 
tention upon the contents and details 
of such films. 


Morelite announces a stereopticon at- 
tachment with their latest model MON- 
ARC lamp, burning Suprex carbons, the 
only lamp of its type so equipped. Lack 
of space with this type of lamp prevents 
its attachment between the front of lamp- 
house and projector. Morelite's stere- 
opticon is attached to the left-side door 
through an opening of which it receives 
its reflected light-beam from a Moroni 
metal mirror enclosed in a frame. The 
latter is located inside of lamphouse and 
substitutes for the front dowser when the 
stereopticon is operated. A half turn of 
a knob outside of lamphouse transfers the 
light beam from showing motion picture 
to still picture of slide on screen and vice 
versa, without moving either the lamp or 
the stereopticon. The light beam for the 
latter passes unobstructedly to the screen 
with any type of projector. 

Screen illumination is much brighter 
than that obtained from any other stere- 
opticon whether attached to a low-amper- 
age lamp or employing a bulb. Over- 
heating is efficiently controlled even with 
the largest carbons through a minute move- 
ment of the lamp mirror, thereby permit- 
ting a still to be shown for five to six 
minutes without cracking the glass slide. 
Complete details available from 600 West 
57th St. 


Television Makes Debut At 
San Francisco Fair 

Visitors to the Golden Gate Exposition 
at San Francisco will not only see prac- 
ticable home television demonstrated, 
but will themselves have an opportunity 
to be televised. Radio facsimile, which 
will print news bulletins, pictures and 
other text in the home, will also be 

Visitors to the television studio may 
stand before the television camera and 
be seen and heard by other visitors in 
an adjoining room to whom they will 
also be visible through a glass window. 
In the viewing room, the images will be 
seen in black-and-white on the fluor- 
escent surface of the Kinescope receiv- 
ing tubes, either directly, or as reflected 
from a mirrored surface. These tubes 
are 12 inches in diameter and give an 
image approximately 8 x 10 inches in 

In the studio, on the transmitting end, 
the Iconoscope tube, or electric eye, 
corresponds to the film in an ordinary 
camera, except that the Iconoscope con- 
verts optical images into electrical im- 
pulses. The camera lens focusses the 
subject onto a plate that has been coated 
with millions of miniature photocells. 
These tiny light-sensitive elements store 
up or lose electrical charges that corre- 
spond exactly to the light and dark 
portions of the subject. At the other 



end of the Iconoscope tube is an elec- 
tron gun, which directs a sharply 
focussed beam of electrons onto the 
plate in a rapid back-and-forth motion, 
a line at a time, until it has covered 
the entire surface of the plate, convert- 
ing the image into electrical impulses. 
At the receiving end, the Kinescope 
tube reverses the transmitting process. 
The incoming signals are amplified and 
made to control the intensity of an elec- 
tron beam which bombards the lumin- 
escent surface of the tube. This bom- 
bardment builds up the picture by a 
back-and-forth motion, a line at a time 
for 441 interlaced lines, at such a high 
rate of speed (4,500 miles per hour) 
that the resultant picture looks complete 
to the human eye- at any given moment. 


The perisphere, which in conjunction 
•with the 700 foot Trylon has become the 
symbol of the New York World's Fair, 
has been utilized by RCA sound engineers 
to form the horn of the largest loud- 
speaker ever constructed — a sound reproducer 
so vast that thousands of persons will be 
able to stand at one time at its periphery. 

A battery of 36 high- and low-frequency 
sound reproducers will be installed in a 
large concrete chamber below ground level 
at the base of the perisphere. This cham- 
ber which is entirely concealed from view, 
will effectively couple the reproducers to 
the horn created by the perisphere and 
the surrounding ground surface forming a 
horizontal 360-degree circular speaker. The 
massive unit is designed to cover the 
audible range of sound from 20 to 10,000 
cycles. It will reproduce sounds so low 
that they will be felt rather than heard. 
This 200 foot ball, set approximately 4 
feet above the ground, gives a circular 
horn 100 feet in depth, 4 feet at the 
throat and 100 feet at the mouth opening. 
' Of especial interest will be the sound 
in conjunction with the Theme Show in 
the interior of the perisphere. Twelve 
especially designed 36-inch high fidelity 
loudspeakers will be mounted near the top 
of the ball-shaped interior, projecting 
sound onto the moving platform, on which 
the spectator will view the "World of 
Tomorrow." Music and sound effects from 
this system will be synchronized with the 
picture action. 


The motion picture industry should ex- 
perience a better-than-seasonal improve- 
ment in domestic theatre attendance and 
box office receipts during the 1939 first half, 
reflecting increased consumer, pending 
power, according to a Poor's Survey report. 
Continuing, the report states: 

"Detracting from the- favorable funda- 
mental position, the Government's anti- 
monopoly litigation is proving disturbing. 
Designed to divorce theatres and studios 
and aimed at the elimination of 'block- 
booking' and other trade practices, the Fed- 
eral law suit may be expected to result in 
numerous changes within the industry. At 
this juncture, it is difficult to forecast the 
ultimate outcome. 

"One thing appears logical, however. 
Should motion picture producers be forced 
to eliminate their theatre investments from 
their corporate setups, common share- 
holders would receive their pro rata equity 

through stock distribution. As for 'block- 
booking,' its elimination might prove bene- 
ficial to producers over the long term, in 
that it would force economies and efficiency 
in film production." 

multitude of small amplifiers and curve 
over the top of the vertical drum to meet 
and steady the shaft. 


Free Films for Schools lists alphabetic- 
ally 1400 free films from over 300 sources 
throughout the U. S. Cross references — 
under 60 different headings show at a 
glance what films are available for school 
projects. Physical data of each film is 
recorded, the number of reels, whether 
16mm. or 35mm. and whether sound or 
silent. Gives addresses of sponsors or 
distributors of each film. 

Published at 25c by the DeVry Corpora- 
tion, 1111 Armitage Ave., Chicago, Illinois. 


Of 104 theatre owners who recently mod- 
ernized their houses with National Theatre 
Supply Co. equipment, 40% put the bulk 
of their purchase right in their projection 
rooms, according to President Walter E. 
Green. These betterments in projection 
and sound were, said Mr. Green, the first 
line of offense in drives for more busi- 

Included in the purchases were orders 
for 18 new Simplex E-7's, 36 Super-Sim- 
plex projectors, 22 Simplex Four-Star 
sound systems, 48 pair of Peerless lamps 
and 60 Walker screens. 


"You Can't Take it With You" (Colum- 
bia) won the Academy Award as the best 
production of 1938, the director of which, 
Frank Capra, also won top honors in his 
division. Other awards went to Bette 
Davis, best performance ("Jezebel") ; to 
Spencer Tracy, best performance ("Boys' 
Town") ; to Fay Bainter and to Walter 
Brennan for the best supporting perform- 
ances; to Joseph Ruttenberg for the best 
cinematography ("The Great Waltz") ; and 
to T. Moulton for the best recording job 
("The Cowboy and the Lady"). 


A gigantic sound reproducing system, 
the main unit of which weighs approxi- 
mately twenty tons, has arrived at the 
N. Y. World's Fair for the General Motors 
"Highways and Horizons" exhibit build- 
ing. Capable of delivering 150 different 
descriptive talks at the same time, the 
voice system will be perfectly synchronized 
to 300 comfortable chairs, mounted on a 
continuous moving escalator and each ac- 
commodating two spectators as they tour 
the mammoth 30,000 square foot exhibit 
panorama. Visitors will have the sensa- 
tion of soaring for many miles over vast 
areas of countryside, industrial and moun- 
tainous sections, through towns and cities 
of the future and, by means of the in- 
tricately designed voice instrument, each 
spectator will hear an intimate, personal- 
ized description of the numerous vistas 
at the same time he is viewing the scenes. 

The speaker system is constructed on a 
finely wrought steel drum, 8 feet in diam- 
eter. The drum rises 12 feet into the air 
from a circular base, which houses its 
motor. The drum revolves, carrying shim- 
mery ribbon bands of sound film in front 
of tiny light needles, whose variation is 
no greater than one-thousandth inch. 
Seven main structural supports protect a 


A lecture-demonstration of the new Sim- 
plex E-7 projector was given on Feb. 23 
under the auspices of Rochester, N. Y. 
Local 253 as part of its regular educational 
program. The meeting, which was followed 
by a buffet supper, attracted an attendance 
of more than 100, including members of 
many Western N. Y. State local unions. 
John Krulish and P. A. McGuire were the 
International Projector Corp. representa- 


Muzak, a subsidiary of Warners, sell- 
ing wired radio to restaurants and grills, 
has a new service whereby its own musical 
transcriptions, plus regular radio programs 
from specially selected radio stations will 
be made available to apartment and home 
dwellers in New York at a cost approxi- 
mately that of a telephone. This is di- 
rect competition for radio set manufac- 

Monthly charge for receivers will be 
$3.50 and $5 for a small and large re- 
ceiver, respectively. In addition, Muzak 
has another plan whereby apartment 
dwellers will be offered the choice of four 
leading broadcasting stations in the metro- 
politan area. Reception will be guaran- 
teed without static or fading. 


The Schine Circuit has renewed sound 
service contracts with Altec Service Cor- 
poration for the coming year, covering 105 
theatres in the Middle Atlantic states. 

C. J. Zern has been appointed manager 
of the Kansas City district of the Altec 
Service Corp. with headquarters there. 


A new era in artificial lighting was ini- 
tiated during 1938 with the introduction of 
fluorescent Mazda lamps, hailed as the great- 
est single development of light production in 
many years. The spectral quailty of light 
from the daylight lamp is the closest ap- 
proach to natural daylight that it has ever 
been possible to produce by any artificial 
illuminant at an efficiency even approaching 
that of these lamps; and, similarly; the 
efficiencies with which these lamps produce 
colored light have never been approached 
previously. Colored light is produced in 
hitherto unobtainable pastel tints as well as 
in pure colors. 

The tubular lamps contain a small globule 
of mercury and a small amount of argon gas 
at low pressure, and pre-heated coiled tung- 
sten wire electrodes covered with an electron- 
emissive material. The low-pressure mercury 
arcs produce ultra-violet radiation which 
activates the fluorescent chemicals, or phos- 
phors, with which the inside surfaces of the 
tubes are coated. The phosphors are energy 
transformers— they step the invisible ultra- 
violet radiation down to the visible part of 
the spectrum. By proper selection and 
blending of the phosphors, it is possible to 
produce radiation in practically any desired 
part or parts of the spectrum. Fluorescent 
lamps, available only a few months, already 



have found applications in many different 
lighting fields. 

A new mercury lamp surpasses in bril- 
liancy most known illuminants: the arc 
attains a brightness of the order of 30,000 
candles per sq. cm. Highest in wattage and 
smallest in size of all the mercury lamps, 
the new 1000-watt water-cooled lamp, with 
an efficiency of 65 lumens per watt, is a 
quartz capillary tube about 3 inches long, 
containing a small amount of mercury and 
fitted at each end with a brass ferrule for 
electric contact. 

The arc stream itself is less than an inch 
long and scarcely larger in diameter than an 
ordinary pin. The intense heat generated by 
such an arc would melt even the quartz tube ! 
almost immediately if some effective method , 
of removing the heat was not employed; the i 
arc tube is operated in a rapidly-moving \ 
stream of water within a glass water jacket. 

This new lamp promises to make an 
important place for itself in the fields of 
photoengraving and blueprinting. It requires 
less current than do other light sources used 
in photoengraving, produces superior work 
because of the steadiness of the arc, and 
makes it possible to produce clean cut en- 
gravings of poster size. For blueprinting it 
makes possible increased printing speeds, 
more compact equipment, and in some cases 
lower wattage*. The lamp is also being 
considered as a light source for searchlights 
of certain types. 

Also introduced during 1938 was a new 
projector lamp in which a reflector of highly 
accurate contour and a lens plate are actu- 
ally parts of the lamp itself. 


Repeal of the No. Dakota theatre-divorce- 
ment law will block consideration of the 
constitutionality of this statute by the U. S. 
Supreme Court, to which an appeal was taken 
by the affected producers and distributors. 
Whether the repeal action will prevent or 
merely retard divorcement is a moot question, 
although there is apparent in producer-dis- 
tributor circles a noticeable trend toward the 
grouping of circuit theatres under separate 
theatre-operating corporations. 

This latter action would not disturb the 
Labor setup in the circuit theatre field, since 
actual control would continue to be vested in 
the real owners— producers and distributors 
—irrespective of theatre-operating personnel. 
That which will really affect circuit theatres 
is the anticipated modification, at least, of 
existing block-booking practices and a drastic 
change in clearance schedules. 


{Continued from page 15) 
ing to the laws of subtractive mixture. 
In the application of light, wide use 
is found for both the additive and sub- 
tractive methods. 

• Producing Colored Light 

Gaseous tubes are coming into wide 
use for the production of colored light. 
Filters which absorb all the colors ex- 
cept the one desired from an incan- 
descent source are also widely used for 
this purpose. For example, if red light 
is to be produced, white light is passed 




Alert Projectionist 
Keeps Sound Going 
by Novel "Haywiring 

"Stage speakers have failed! Get an inspector here right away!" 

That was the emergency call received from a theatre in Virginia 
by the local Altec office. 

When the Altec man arrived at the theatre he was astounded 
to find that the show was still going on, sound and all, to the satisfac- 
tion of a good-natured audience— even though the stage speakers 
were completely dead! 

After the stage speakers had failed, and the Altec man was 
called, the projectionist didn't "sit on his hands" awaiting help. 
Thinking fast, he moved the projection room monitor horn from 
its usual location and placed it at a porthole, projecting the sound 
from the monitor horn into the auditorium! 

This striking example of ingenuity on the part of a projectionist 
kept the show going until the trouble could be cleared. 

In thousands of theatres throughout the country, projec- 
tionists and Altec service inspectors work in harmony 
to keep the sound projection at constant peak perform- 
ance. The spirit of cooperation with which projectionists 
and Altec men do their work is an important factor in 
providing the full entertainment value of motion pic- 
tures to millions of theatre patrons daily. 



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through a red-colored filter. Various 
substances are used for filters such as 
glass, gelatin, lacquer, fabric and pig- 
ments. The choice of color media is 
determined by the manner in which they 
are to be used, and the desired perman- 
ency of the installation. 

In another method of producing 
colored light which will probably play a 
large part in the lighting of the future, 
fluorescent materials are used in conjunc- 
tion with light sources such as the low- 
pressure mercury arc. With sources of 
this kind, it is possible to produce from 
fifty to two hundred times as much light 
as can be obtained by filtering the light 
from an incandescent lamp. 

At times it is important to repro- 
duce the color quality of average day- 
light for purposes of proper identifica- 
tion or matching of colored objects. 
For example, it is usually desirable to 
see the daylight appearance of fabrics, 
even though they be viewed at night. 

For reproducing daylight, a blue 
color filter may be used with an in- 
candescent lamp, allowing the trans- 
mission of only the proper proportion 
of each wave band to give the desired 


Already assured of all 35 mm. projector 
jobs at the forthcoming World's Fair in 
New York, Local 306 is pressing hard 
for 16 mm. unit jobs on the Fair grounds. 
Four 16 mm. projectors are regarded by 
Local 306 as a unit, with one man per 
unit. Tentative scales compare favorably 
with those paid on 35 mm. jobs. 

color quality of the transmitted light. 
For approximate results the daylight 
lamp or enclosing globes of blue glass 
may be used, but wherever accurate 
identification must be made or if the 
results must be scientifically repro- 
ducible, special color filters must be 
used; they may be obtained commer- 

• Psychology of Color 

In spite of an apparent relationship 
between color in both pigment and 
light and human behavior, definite 
scientific facts on the subject are few. 
The illuminating engineering profession 
has been hesitant about accepting as 
scientific theory certain interesting re- 

actions which many observers have 
duplicated from time to time but as 
yet not invariably enough to develop a 
definite psychology of color. 

However, a review of these few in- 
vestigated facts relative to color and 
its effects on human reactions should 
prove interesting to the illuminating 
engineer even though, as yet, they can- 
not be given the benediction of science. 

Many investigations over a period of 
years have indicated a marked differ- 
ence in color preference between men 
and women. Men prefer blue and 
women red, when color in the abstract 
is involved, disassociated from current 
fashions and other factors that might 
prejudice the subject. Investigation 
shows, however, that the second choice 
for men is red; while that for women 
is blue; hence this preference is marked 
but not always definite. 

Both sexes, however, react favorably 
to bold colors and show definite prefer- 
ence for strong primary colors of great 
vividness when these again are dis- 
associated from current fashions in 
dress or other factors likely to affect 
the selection. This fact is of great 
significance in advertising and decorat- 
ing to attract attention, and is another 
reason for the predominance of such 
colors in outdoor advertising, in addi- 
tion to the advantage of their greater 
distance visibility when properly used. 

• Contrast and Variety 

It must be emphasized that, in the 
foregoing section, colored pigments 
alone were considered, for when colored 
lighting is investigated, almost the ex- 
act opposite in preference of men and 
women is noted. Men like the warm 
colors of light, the yellows and am- 
bers for instance; and women like the 
cold colors of the spectrum. The 
theatre and the displayman frequently 
make use of this knowledge in their 

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efforts to influence people. Again it 
must be pointed out that this noted 
preference is with colored light in the 
abstract, and that in practice, contrast 
and variety arc important factors in 
using color in a pleasing manner, re- 
gardless of the sex of the observers. 

The use of the adjective "warm" to 
describe red, amber, and yellow light, 
and "cool" to designate blue, green, 
and bluish-white light, is very significant 
for it is a matter of general observation 
ihat rooms lighted in the former colors 
give observers a definite feeling of 
bodily warmth; while rooms lighted in 
the latter colors "feel" cool. These 
facts are frequently used in interior 
lighting, changes being made in the 
color lighting for winter and summer. 
Again the displayman would do well 
to follow suit, using light of a cool 
nature on refrigerator displays, and 
warm colors of light on bathing suits, 
by way of example. 

Moreover, yellow and amber tinted 
light is definitely stimulating, and has 
been known to increase the pulse rate 
of the more emotional types of people; 
while bluish-white, and other cool 
colors of light are restful and soothing, 
provided the color is not too strong and 
definite. Purple and violet light are 
depressing and uncomfortable to a 
marked degree. 

In fact, the human race as a whole, 
men and women, do not like bold, 
vivid colors in lighting, regardless of 
the wavelength employed. They do 
like, however, tinted light, and in the 
future the color of the light will un- 
doubtedly play an increasingly impor- 
tant part in the home, factory, and 
store, as well as in the theatre and 
for display where already it is used ex- 
tensively and to advantage. 


(Continued from page 10) 

even when no sparking is visible at the 
trailing edge. 

Dull markings in the central portion 
of commutator segments, parallel to the 
edges, are sometimes caused by this 
sparking underneath the brushes. In 
the presence of a high-resistance glaze, 
such sparkling punctures the commu- 
tator film and is one cause of the small 
spots of bare copper sometimes seen on 
an otherwise uniformly glossy surface. 
This localized breakdown of the film re- 
leases particles of copper which may 
become imbedded in the brush faces 
and cause streaking of the commutator 
surface. The localization of current 
which follows such streaking often ne- 
cessitates resurfacing of the commutator 
in order to restore normal conditions 
and satisfactory brush performance. 

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At Independent Theatre Supply Dealers Everywhere 
In Canada: Dominion Sound Equipments, Ltd., Montreal, Quebec 


47-31 Thirty-Fifth St. 

Long Island City, N. Y. 

Humidity has been found to have a 
noticeable influence on the performance 
of metal-graphite slip ring brushes. 
During winter periods of extremely low 
humidity, excessive dusting and rapid 
wear of slip ring brushes is of frequent 
occurrence. Air conditioning has been 
utilized to overcome this trouble. The 
effect of humidity on commutator 
brushes is less marked than on slip ring 
brushes and some undesirable effects 
may result from high humidity. 

Humidity probably has a favorable 
effect on friction as long as an unbroken 
surface film is maintained on the com- 
mutator. However, there are indications 
that excessive humidity may be a source 
of electrolytic action under the brush 
face, causing deposition of copper on 
the faces of the cathode brushes, that 
is. the brushes receiving current from 
the commutator or slip ring. If this 
effect is sufficiently pronounced, the im- 
bedded copper may break up the com- 






Forest Rectifiers are more than 
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They are designed for motion pic- 
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mutator film, impair commutation and, 
in severe cases, cause commutator 

Temperature undoubtedly has a pro- 
nounced influence on brush perform- 
ance. However, the most important 
effects of temperature are probably 
transient in character, that is, they are 
related to the highly localized tempera- 
ture conditions momentarily established 
at the points through which current 
passes between brush and commutator. 
As previously pointed out, these local- 
ized areas of current transfer are of 
three types: points of solid contact be- 
tween the carbon brush and the com- 
mutator surface, contacts established by 
bridging particles of conducting mate- 
rial, and points at which current passes 
in the form of minute arcs. 

Very high local temperatures exist at 
the points where arcing transfer occurs, 
somewhat lower temperatures at the 
points of particle contact, and still 
lower temperatures at the points of solid 
contact. Even at the latter points, how- 
ever, transient temperatures attain a 
value much higher than the average in- 
terface temperature which is, itself, con- 
siderably above average commutator 
surface temperature. 

It seems probable that these local 
temperatures at times reach values at 
which ionization of surrounding mate- 
rials and gases exerts an important in- 
fluence on commutation phenomena. 
However, since these points of extreme 
temperature are underneath the brush 
face and so highly transitory in char- 
acter, it is extremely difficult to analyze 
the exact nature of their effect on brush 

Obviously, the average temperature 
of the commutator has an influence on 
factors such as commutator distortion, 
loosening of segments and surface oxi- 
dation, but, in respect to interface con- 
ditions, it has little influence beyond 
establishing the temperature plane upon 
which the much higher transient tem- 
perature conditions are superimposed. 


{Continued from page 13) 

about 50 to 1 for large areas and 10 
to 1 in details. Experimental Kine- 
scopes have been built in which the 
luminescent screen is deposited on a. 
thin sheet of glass which is mounted 
inside a transparent glass bulb. Such 
tubes are capable of a considerably 
greater range between large areas and 
in details. 


Mr. Crabtree: When televising an out- 
door subject, what is the threshold light- 
intensity necessary for reproduction, as com- 
pared with that necessary when photograph- 
ing with an f/2 lens in combination with the 
high-speed film emulsion we now have 
available ? 

Mr. Beers: With various standard and 
special pick-up tubes, we can get pictures 


Tests show that 
light begins one-third of the dis- 
tance from the center of the pic- 
ture area and increases sharply 
to a Ught loss greater than 33 1/3% 
at the sides. This loss is elimin- 
ated in the Even-Lite Screen. 


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under any lighting conditions in which 
you can take pictures on film. 

Mr. Crabtree: In other words, you 
can reproduce satisfactoily a football game 
about half an hour after sunset on a rainy 

Mr. Beers: Yes. We have obtained 
recognizable pictures in which the sub- 
ject had a surface brightness of 1 or 2 

Mr. Carver: I do not understand 
whether you have a flicker blade or not, 
or whether it is or is not necessary. 

Mr. Beers: There is no flicker blade, 
as such. A flicker blade is not necessary 
in television, due to the way in which 
we reconstruct the image. We produce 
on the end of the tube a certain num- 
ber of images a second, and that controls 
the flicker. Nothing in the projector has 
anything to do with the manner in which 
the images are actually reproduced. 

Mr. Carver: What do you do when 
the film is being pulled down? There is 
no picture on, and there must be a dark 

Projection Process Limitations 

Mr. Beers: You are actually seeing the 
picture when the film is being pulled down. 
During the pull-down we scan the elec- 
(rical image that remains on the mosaic of 
the Iconoscope. That is when we see 
the image at the receiver. The picture 
is projected when nothing is seen at the 
receiver. That is the interval in which we 
transmit the synchronizing signals. 

We have two choices in television. One 


FS Condensers are ground and 
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FS Reflectors are accurately 
made for correct focus, individu- 
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protected by a heat-resisting re- 
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are, of course, guaranteed to give 
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is to attempt to scan the picture on the 
mosaic of the Iconoscope during the time 
the picture is actually being projected 
there. That means then that we have to 
pull down the next frame of film during 
the time we transmit our scanning sig- 
nals, which is approximately 1/800 of a 
second. That imposes some physical re- 
quirements on a projector we have not 
been able to meet. We have not been 
able to conceive of a projector on which 
the frame can be pulled into place in 
1/800 second without tearing the film. 

The easier way is to pull the film into 
place in the gate during the long interval 
of time and to project it on the Icono- 
scope mosaic during the short time inter- 
val; and then to scan it, while the optical 
image is no longer on the mosaic, using 
the electrical image that is stored there. 

Mr. Friedl: Reference was made to 
mechanical systems in England and the 
speeds with which these systems operate. 

Can someone throw some light on the 
question of mechanical system vs. the elec- 
tronic systems? 

Mr. Goldsmith: The electronic systems 
offhand seem to be most appropriate be- 
cause electrons are weightless and are 
readily controlled in flight and form a 
sort of "air-brush" for painting pictures 
which can be moved rapidly and readily. 
The only mechanical system that seems 
to be seriously considered commercially 
today, at least in England, is the one Mr. 
Kaar mentioned, the Scophony system, in 
which essentially there is a storage capac- 
ity, because of a diffraction phenomenon 
of standing waves of supersonic frequency 
in liquid, actuated by a vibrating quartz 
crystal. In this system one may scan a 
half line at a time (about 200 picture 
elements) . 

This system, however, as Mr. Kaar 
pointed out, employs a motor running at 
some 30,375 revolutions per minute for the 

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high-speed or line deflection of the spot, 
and a smaller motor, running at a lower 
speed, for the frame scanning, two mirror 
systems, the supersonic cell, some lenses, 
and a mercury-vapor capillary lamp for 
the light-source. The picture produced is 
18 x 24 inches in size. 

The competitive devices in England are, 
for example, the Phillips receiver which 
produces an 18 x 24-inch picture by pro- 
jection from approximately a 3-inch pro- 
jection type cathode-ray tube. 

The prices on the British market today 
are $850 for the Phillips receiver produc- 
ing the 18 x 24-inch picture, and some- 
thing over $1100 for the comparable Sco- 
phony receiver, but nobody has given re- 
liable data as yet as to the relative per- 
formance, life, and economics. 

The receivers in England run in the 
price range from $125 to $150 (for the 
picture only) in a chair-side type. Re- 
ceivers for larger pictures run up to $300 
_ or $400, with top figures of $1200 for very 
large pictures (18 x 24 inches) with sound 
and all sorts of extra attachments, phono- 
graphs, and the like. 

Mr. Beers: If it were economically pos- 
sible to use 24 frames in television it 
would be done. It is theoretically pos- 
sible, but the increased amount of filter- 
ing and shielding necessary in the receiver 
to make it perfectly satisfactory from the 
standpoint of eliminating the moving 
images resulting from the 60-cycle power- 
supply system make it economically im- 

Mr. Roberts: When scanning 24-frame 
motion pictures at 60 or 30 cycles, do you 
get any time-distortion in the presentation 
of the picture? Would there be any un- 
expected effect as a result of seeing one 
frame longer than the one before it? 

Mr. Beers: We have noticed no more 
distortion than is normally noticed in mo- 
tion pictures. 

Pickup Method Elective 

Mr. Crabtree: Do you think the trend 
will be to record directly by means of 
television scanning, or that the subjects 
will be photographed on motion picture 
film previously to scanning? What are 
the relative merits of the two processes 
— direct scanning and transmission at the 
scene, as against photographing the scene 
and then bringing the film to a central 
transmitting station. 

Mr. Beers: That is a program prob- 
lem. Either can be done. The scene may 
be taken on motion picture film and then 
converted into television program mate- 
rial; or, as you know, we have a mobile 
unit which can be taken out to the scene 
and there televise it and transmit its pic- 
ture directly by relay to the transmitting 

Mr. Schlanger: Am I to understand 
that the television picture is equal in 
quality to a 16 mm. picture projected 
with a 250-watt lamp and of comparable 
size and viewing distance? 

Mr. Beers: From the standpoint purely 
of picture detail they would be comparable. 
I stated that the film was processed to 
produce duplicate films. If you take stand- 
ard home motion picture on reversible film, 
you will have somewhat better detail, but 
with ordinary commercial processing of 
duplicate films, I think that the picture 
detail of the two will be comparable. 



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Get spare photocells for your 
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Visitron cells are available for every type of sound projec- 
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Many theater patrons prefer the back seats. 
They enjoy the added eye comfort which distance 
gives when viewing rapid action on the screen. 
However, they desire sufficient screen illumina- 
tion for easy vision. They are critical but, for 
this very reason, are likely to become regular 
patrons of the theater that provides the type of 
projection they enjoy. 

With old style, low intensity projection there 



is often insufficient screen light for ease of vision 
much beyond the center of the auditorium. 
Patrons in the rear find vision an effort, and may 
seek their screen entertainment elsewhere in the 
future. Simplified High Intensity projection 
provides screen illumination that insures com- 
fortable vision to every patron in the house. 

Ask your dealer's salesman to show you how 
little it costs to satisfy the "back seat patrons." 





" poo aaaaaaoaaaoa aaaoo aaaai 

The ivo-rh "National" and "Suprpx" are tradp-marls of National Carbon Company, In 


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General Offices: 30 East 42nd Street, New York, N. Y. 

MARCH 1939 


THE SCREEN Makes Triumphant Debut! 

New Magic Voice of the Screen with Rotary 
Stabilizer Plus Shock-Proof Drive! 

1. Push-pull adaptability. 2. High frequency cellular speakers. 
3. Large size, low frequency speakers. 4. Emergency stand-by. 
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tus oiling. 10. Economical operation. 11. Low cost maintenance 

— liberal service. 12. Easy payment plan. 

RCA Photophone's Service Organization has a low cost theatre 

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Remember . . . More than 5,0(JU theatres from coast to coast use 

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Scoring a smash hit with motion picture fans at the 
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New styling ... new convenience... new protection added reserve power... it offers the kind of 
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Listen to the Magic Key Sundays, 2 to 3 P. AL, E. S. T., on NBC Blue Network 
Better sound means better box office— and RCA Tubes mean better sound 






©C1B 4130 

APR -1 1939 


Edited by James J. Finn 

Volume 14 ( 

MARCH 1939 

Number 3 

Index and Monthly Chat .... 5 

An Analysis of Brush Operation 
on Commutating Equipment . . 7 

National Carbon Company 

A British Estimate of Theatre 
Television 10 

R. Howard Cricks 

Changeover Signal Devices . . 11 
Henry Behr 

New Forms for Electrical Data . . 12 
Aaron Nadell 

Television, Sound Recording to 
Feature S.M.P.E. Program. . . 15 

Sixth Subscription Contest Dia- 
gram; Only Two Winners .16 

Addendum to Cooperative Work 
by Projectionist and Service- 
man 17 

Leroy Chadbourne 

Ohm's Law and its Application 
to Some Projection Problems. 
John H. Hertner 

New Background Process Pro 





Major N. Y. Strike Looms; I. A. 

Demands Exchanges Deny 

Film to Non-I. A. Theatres; 

Legal Angles 20 

James J. Finn 
News Notes 
Technical Hints 
Miscellaneous Items 

Published Monthly by 



Circulation Manager, Ruth Entracht 

Subscription Representatives 

Australia: McGills, 183 Elizabeth St., Melbourne 
New Zealand: Te Aro Book Depot, Ltd., 64 Courtenay Place Wellington 
England and Dominions: Wm. Dawson & Sons, Ltd., Pilgrim St., London, E. C. 4. 

Yearly Subscription: United 
States and possessions, $2 (two 
years, $3 ) ; Canada and foreign 
countries, $2.50. Single copies, 
25 cents. Changes of address 
should be submitted two weeks 
in advance of publication date to 
insure receipt of current issue. 
Entered as second-class matter 

February 8, 1932, at the Post 
Office at New York, N. Y. under 
the act of March 3, 1879. 
Contents copyrighted 1939 by 
James J. Finn Publishing Corp. 
International Projectionist 
is not responsible for personal 
opinions appearing in signed 
articles in its columns. 

Monthly Chat 

PRODUCTION schedules for the 
coming film season indicates a sub- 
stantial boost in the number of color 
prints, including short subjects. Which 
news is most welcome. We observe in 
passing, however, that Technicolor states 
that the density of its prints is control- 
led to produce "a satisfactory screen 
image when light falling on the screen, 
measured with the projector operating 
without film, is approximately ten foot- 

Now, just what reading in foot- 
candles this will insure even in theatres 
having modern arc lamps we can't figure 
out at the moment, but we'll wager that 
it falls far short of approved practice. 
At the moment we're focusing on those 
5000 theatres which still use low-inten- 
sity lamps, the result of which is to make 
a color print a travesty on efficient pro- 
jection. To what avail does Hollywood 
wallow in an ocean of Technicolor 
prints — at about twice the cost of black- 

• • • 

Bausch & Lomb Optical Co. will an- 
nounce shortly a new series of vastly 
improved projection lenses which are 
expected to give more and better light. 
These lenses, one of which may be an 
/1.9, are expected to soothe the feelings 
ot those projectionists who clamor for 
better optics as a means for increasing 
light output to the screen. Of course, 
improved optics is only one angle of this 
many-sided problem — but it definitely 
won't clean a dirty screen. 

• • • 

Three projectionist fatalities during 
the past five weeks as a result of theatre 
film fires. Oklahoma Supreme Court 
please note. Incidentally, what is the 
state or district organization doing 
about this august body's recent decision 
that projection is a "non-hazardous 

• • • 

Many recent releases attest to the 
need for compliance by Coast studios 
with the request of the SMPE Projec- 
tion Practice Committee that a margin 
of safety be allowed when shooting a 
picture so that the heads and feet of 
actors, and other content, not be cut 
off. Cameramen still insist upon shoot- 
ing to the extreme limits of the aper- 
ture, with results that are all too appar- 
ent to require extended comment herein. 

• • • 

JOTTINGS: Avoid signing for tele- 
vision "courses" before careful in- 
vestigation . . . We are preparing a little 
table showing the utter futility of 
operating Suprex arcs as much as 10 
amperes above approved rating — ■ for 
those doubters who, without any sup- 
porting evidence, disputed our earlier 
remarks anent this topic . . . Coming 
up: more studio stuff, including that 
much-requested data on the course of a 
print from camera to theatre. Also, a 
new series on math, written especially 
for you, Mr. Projectionist. 

MARCH 1939 


EASTMAN'S new motion picture negative 
films . . . general-purpose Plus-X, high- 
speed Super-XX, ultra-fine-grain Back- 
ground-X . . . add highly dependable per- 
formance to extraordinary special abili- 
ties. Their instant acceptance and con- 
stantly wider use by the industry mark 
them as today's outstanding raw-film stars. 
Eastman Kodak Company, Rochester, N. Y. 
(J. E. Brulatour, Inc., Distributors, Fort 
Lee, Chicago, Hollywood.) 

Super-XX ... Background-X 





MARCH 1939 

An Analysis of Brush Operation 
on Commutating Equipment 



BRUSH friction is an item of major 
importance in relation to brush 
performance affecting, in substan- 
tial degree, the total mechanical energy 
loss of the machine, the commutator 
temperature and the quietness of opera- 
tion. Since friction results from the 
relative motion between the commutator 
surface and the brush face, anything 
which affects either surface, or the inti- 
macy of contact between these surfaces, 
has an influence on the friction exper- 
ienced in operation. Consequently, the 
study of brush friction is complicated 
by many factors difficult to define and 
even more difficult to control. 

Perfectly smooth surfaces, sliding one 
upon the other, represent an ideal con- 
dition never realized in practice. Inter- 
locking of microscopic irregularities in 
the contacting surfaces is, possibly, the 
primary source of frictional resistance. 
In this instance the magnitude of the 
friction loss depends upon the ease with 
which these points of interference can 

be broken away from one surface or 
the other or allowed to ride over one 
another as a result of deformation or 
separation of the surfaces. 

Hard particles, imbedded with suffi- 
cient firmness to resist displacement, 
cut their way through the contacting 
surface. This, together with similar 
action by free particles of sufficient 
hardness, is the source of mechanical 
abrasion. Abrasion resulting from firmly 
imbedded particles naturally increases 
the friction loss, and, for this reason, 
most abrasive brushes show a high co- 
efficient of friction. 

With soft, graphite brushes, however, 
a low coefficient of friction may be ob- 
served in the presence of appreciable 
abrasive action. Natural graphites con- 
tain a certain amount of gritty material, 
not all of which is removed in the refin- 
ing processes applied to commercial 
grades. These gritty particles are the 
source of the abrasive action frequently 
observed with natural graphite brushes. 
However, due to the relatively weak me- 

chanical structure of graphite, the points 
on the brush face which interlock with 
irregularities of the commutator surface 
break away with little resistance. 

Furthermore, as loosened particles of 
graphite undergo the shearing action 
produced by the motion of the commu- 
tator under the brush, they continue 
to break down into smaller and smaller 
particles, filling up minute surface irreg- 
ularities and enabling protruding points 
to ride over one another with relative 
ease. In this manner, the graphite acts 
as a lubricant between the contacting 
surfaces, maintaining low friction even 
in the face of appreciable abrasion. 

The effect of free particles under the 
brush face may be either favorable or 
unfavorable with respect to friction, de- 
pending on the nature of the particles. 
Consider an iron casting being dragged 
over a concrete floor. The friction is 
high but, if ashes are thrown in front 
of the casting, it can be dragged more 
easily. This is because the ashes fill up 
some of the irregularities in the surfaces 

MARCH 1939 


and offer little resistance to further pul- 
verizing from the shearing action pro- 
duced by motion of the casting over the 

If marbles were placed under the 
casting, resistance to motion would be 

unequal distribution of current among 
the different brushes on the machine. 

There is also a limited range of pres- 
sure within which best brush perform- 
ance is obtained. If the pressure is too 
light, imperfect contact with the com- 





Relationship of brush 
pressure and rate 
of brush wear for 
lampblack base, elec- 
trographitic grades 

2 3 






still further reduced by the rolling 
action of the marbles. Irregular frag- 
ments of glass or stoneware, on the 
other hand, by increasing the number 
of points of interlocking contact be- 
tween the casting and the floor, might 
make the resistance to motion greater 
than that experienced on the bare floor. 

Graphite particles between brush and 
commutator, as previously described, re- 
duce friction in the same manner as 
ashes thrown on the floor. Particles of 
substantially uniform diameter, freed 
from either the brush or the commutator 
surface, may, like the marbles, reduce 
friction by their rolling action. Hard 
particles of irregular shape may, on the 
other hand, result in higher friction. 

Among the many advantages of lamp- 
black base, electro-graphitic brushes are 
these: they do not contain gritty par- 
ticles to abrade the commutator; they 
contain sufficient graphite to provide 
lubrication and to aid in the development 
of a desirable surface film on the com- 
mutator; the extreme fineness of the 
lampblack particles tends to reduce fric- 
tion by rolbng action when these par- 
ticles are loosened from the body of 
the brush; finally, the firmness of bond- 
ing prevents protruding points being 
broken off in jagged form and allows 

mutator is liable to result. This is a 
frequent source of sparking, injury to 
the commutator surface and undue 
brush wear. Excessive brush pressure 
results in unnecessary friction, needless 
wear, and, under certain conditions, may 
even reduce the stability of the brush 
position in its holder and against the 

There is a reasonably wide latitude 
of pressure within which satisfactory 
performance can be expected. The lim- 
iting values of this optimum range vary 
with different types of brushes, but no 
difficulty from this source need be ex- 
pected if the recommendations of the 
brush manufacturer are followed. 

Brush wear is not necessarily reduced 
by reduction of brush pressure. In fact, 
at pressures appreciably below the re- 
commended optimum range, brush wear 
increases very rapidly. Electrical causes 
predominate as the source of brush 
wear at low temperatures. Increased 
brush wear is also encountered at pres- 
sures above the maximum recommended 
but the rate of increase is less for pres- 


3 for lampblack base, electro-graphitic 
grades. Similar effects may be observed 
with all grades of brushes, but the range 
within which best performance is ob- 
tained is different for different grades. 

• Commutation Factor 

Frequent mention has been made of 
the importance of firm contact between 
the brush and the commutator. The 
nature of the surface film on the com- 
mutator, atmospheric conditions, fric- 
tional properties of the brushes, brush 
pressure and angle of indication to the 
commutator all have an influence on the 
intimacy of contact at the brush face. 

Another factor, possibly more im- 
portant than any of the foregoing, is 
the elastic property of the brush. It is 
subject to accurate, quantitative deter- 
mination and, because of its direct in- 
fluence on commutating performance, is 
defined as commutation factor. Several 
years of experience with applications 
under widely varied conditions of service 
have demonstrated the importance of 
this property in respect to brush opera- 

By selecting a brush of suitable com- 
mutation factor, intimate contact be- 
tween brushes and commutator can be 
maintained, with good commutation and 
quiet operation, in the face of disturb- 
ing conditions that could not readily be 
overcome in any other manner. 

• Contact Drop 

Contact drop has long been the criter- 
ion by which the commutating proper- 
ties of a brush are judged from an anal- 
ysis of characteristics determined in the 
laboratory. However, there is good 
reason to believe that other character- 
istics, such as reasonably low coefficient 
of friction, good commutation factor and 
ability to maintain a good surface film 
on the commutator are of equal import- 
ance in avoiding injurious sparking. 

The importance that has been placed 
on contact drop is largely based on the 
assumption that, inasmuch as some volt- 
age is present in the short-circuited coils 
of the armature during the commutating 
period, current must flow during the 
entire period of short-circuit through the 
brush face from segment to segment par- 

them to be worn into conformity with Conventional diagram illustrating £ 

the general contour of the contacting 

• Brush Pressure 

The pressure at which brushes are 
held in contact with the commutator is 
a matter which should be given careful 
attention. The pressure should be equal 
on all brushes to avoid the difficulties 
arising from selective action, that is, 

commutation interval 





sures above the optimum range than it 
is for those below. 

At high pressures, mechanical wear 
predominates. This relationship of pres- 
sure to brush wear is illustrated in Fig. 

allel to the commutator surface — that is, 
through the thickness of the brush. 

Since the electrical resistance through 
the armature coil, the segments and the 
short path through the face of an ordin- 



ary carbon or graphite brush is low, it 
is further assumed that the voltage drop 
through the resistance of the two seg- 
ment-to-brush contacts, included in this 
short-circuit path, must approximate the 
voltage in the coil if excessive short- 
circuit current is to be avoided. 

This theory has led to the develop- 
ment of various special types of brushes 
having a laminated structure or very 
high cross-resistance to aid in the control 
of this short-circuit current. The error 
in this theory is that it overlooks the 
fact that, in addition to the current 
from the short-circuited coil under con- 
sideration, current is flowing in each 
segment to or from an adjacent coil to 
which it is connected. 

If the commutating conditions of the 
machine are correctly compensated, by 
brush position or properly adjusted in- 
terpole field, current flows in only one 
direction between commutator and brush 
and there is no short-circuit current in 
the brush face. This is shown by the 
fact that, on a properly adjusted ma- 
chine, the voltage drop between brush 
and commutator shows no reversal of 
direction at any point from leading to 
trailing edge. However, in the case of 
over or under compensation, reversal of 
voltage will be observed and, in such 
cases, short-circuit current will flow in 
the vicinity of that portion of the brush 
face where the normal direction of volt- 
age is reversed. 

Although there is no actual short-cir- 
cuit current in the brush face under 
good commutating conditions, it some- 
times simplifies the analysis of certain 
phenomena of commutation to consider 
the unidirectional current through the 
brush contact as having two components, 
one the load current of the armature 
and the other a localized current 
through the short-circuited coil and the 
brush face. 

It is customary, in discussing prob- 
lems of commutation, to use this method, 



V i 

\ 1 
\ 1 









1 \ 
1 ^ 








\ i LINE 





treating load current and short-circuit 
current as separate and co-existent phe- 
nomena. In the following discussion, 
however, the commutation cycle will be 
analyzed on the basis of resultant cur- 

rent at successive points across the 
brush face. 

The circuit diagram for coils under- 
going commutation is shown in conven- 
tional form in Fig. 4. Fig. 5-A repre- 

Exact repetition of a particular group 
of curves, such as shown in Fig. 5, will 
occur in adjacent coils and segments 
only in an armature with perfect elec- 
trical balance and having only one coil 


A — Curve of com- 
mutation current in- 
dicating over - com- 
pensation. B — Cur- 
rent in commutator 
segment at success- 
ive positions. C — 
Range of current 
density in brush face 


scnts a normal curve of commutation 
current. The ordinates of this curve 
indicate the value and direction of the 
current in coil "a" (Fig. 4) during the 
commutation interval, and the abscissae 
indicate the position of the division be- 
tween segments "A" and "Z" across 
which coil "a" is short-circuited by the 

The current flowing through segment 
"A" as it passes under the brush is in- 
dicated by the horizontal lines in Fig. 
5-B. The lateral location of these lines 
indicates successive positions of segment 
"A" in relation to the brush face, and 
their distance above the zero line rep- 
resents the value of the current flowing 
through the segment at the positions 

The corresponding range of current 
density at various points across the 
brush face, is shown in Fig. 5-C. The 
full cycle of variation between maximum 
and minimum limits of current density 
at any point on the brush face has a 
frequency equal to that at which the 
commutator segments are passing that 

The values of current density here 
represented assume contact with the 
brush over the full surface area of that 
portion of the segment under the brush 


A — Normal curve of 
commutation current 

B — Current in com- 
mutator segment at 
successive positions 

C — Range of current 
density in brush face 

© === 

at any given instant. No attempt has 
been made to evaluate the much higher 
transient current densities encountered 
at the relatively small number of points 
at which contact usually occurs. 

per slot. Where there is more than one 
coil per slot, the second will commutate 
under slightly different field conditions 
than the first, and the third under con- 
ditions differing from both the first and 
second. Therefore, between segments in 
which essentially identical conditions 
recur, there may be one or more inter- 
vening segments in which the cycle of 
commutation is somewhat different. This 
is the reason for the second or third bar 
marking frequently observed on the 
commutators of machines having two or 
three coils per slot. 

Figure 6-A is typical of the commuta- 
tion curve encountered under conditions 
of over-compensation. It will be seen 
from Figs. 6-B and 6-C that reversal 
of current occurs in the segments shortly 
before passing from under the brush, 
with corresponding reversal of current in 
that portion of the brush face. Under 
such conditions intermittent short-cir- 
cuit current flows in the brush face near 
the trailing edge, and a voltage drop 
curve across the brush face shows re- 
versal of direction near the trailing 

With under-compensation similar ef- 
fects are encountered near the lead- 
ing edge of the brush. In a machine 
with three coils per slot it is entirely 
possible for one coil to be under-com- 
pensated during commutation, the next 
properly compensated and the third 

It will be noted in Figs. 5 and 6 that 
the highest current density in the brush 
face occurs at the same point as the 
most rapid change of current in the coil 
undergoing commutation. This fact, 
together with the increase of contact 
drop which accompanies this rapid 
change of current, may cause injurious 
sparking even when, as in Fig. 6, this 
condition is encountered at a point un- 
derneath the brush and, therefore, is 
not indicated by visible sparking. 

The extremely wide range of fluctua- 
tion in local current density, indicated 
near the central portion of the brush 
face in Fig. 6-C, may also be a source 

MARCH 1939 

of concealed sparking and brush face 

It should not be assumed from the 
foregoing discussion that contact drop 
is without value in respect to brush per- 
formance. Appreciable contact drop, 
or, in other words, contact resistance, is 
needed to assist the impedance of the 
coil in controlling short-circuit current 
under conditions of imperfect compen- 
sation. Reasonable contact resistance 
probably tends to improve the commu- 
tation cycle, preventing overly rapid 
transfer of current from a segment 
already under the brush to one just 
making contact, and also helping force 
current from a segment about to break 
contact with the brush into those still 
making full contact. 

Where uniform surface conditions are 
maintained on the commutator, and the 
contact resistance of all brushes of like 
polarity is essentially the same, the fact 
that contact resistance constitutes the 
principal resistance in the several par- 
allel paths tends to stabilize current dis- 

tribution between the brushes and min- 
imize selective action. 

• Summary 

It is difficult to say what is the most 
important property in a carbon brush. 
The characteristic which makes a brush 
the ideal selection for one application 
may be of secondary importance to some 
ether property on another machine. For 
heavy-duty service it seems probable 
that those characteristics which aid or 
permit the development and mainte- 
nance of a uniform surface film on the 
commutator are of greatest importance. 
The relative importance of individual 
characteristics, for any particular appli- 
cation, depends upon the unfavorable 
factors which must be overcome. From 
the large number of such factors men- 
tioned in the foregoing discussion and 
the varying influence each may exert on 
different applications it is easy to under- 
stand why the "universal brush" has not 
yet appeared and probably never will be 

A British Estimate of Theatre Television 



CINEMA television is here. A fort- 
night ago I, in a wildly enthusiastic 
audience of nearly 2,000, saw in the 
Marble Arch Pavilion a fight taking 
place at Harringay Arena; at the newly 
opened Monseigneur next door, and at 
the Tatler, Charing Cross Road, packed 
audiences simultaneously watched the 
same event. 

The Baird equipment at the Pavilion 
and at the Tatler was, of course, of the 
projected cathode-ray image type, at the 
former on a 15-ft. screen and at the 
latter on a 12 ft. 6 in. screen. From 
studio transmissions the quality of the 
picture was inferior to the average news- 
reel only in being less bright, although 
the ringside transmission was hardly 
good enough. 

After the fight I dashed next door 
into the Monseigneur and saw the rest 
of the transmission there. The Sco- 
phony equipment embodies, of course, 
mechanical scanning, giving an 8-ft. pic- 
ture. S. Sagall, (head of Scophony) 
told me earlier in the day that, had time 
permitted, he could have installed his 
newest equipment, with improved optical 
system, giving a 16-ft. picture. 

• Extension to Provinces 

Following upon the Pavilion show, 
Isidore Ostrer (president of a theatre 
chain) spoke of equipping the whole 
of the G.-B. circuit with large screen 
receivers, on the assumption that by the 
time their hundred London theatres are 

equipped, provincial television services, 
by means of the coaxial cable, will have 
become a reality. Even to the London 
theatres, cable rather than radio trans- 
mission might, I suggest, prove advan- 

What does this advance mean? Is the 
film, or at any rate the newsreel, 
doomed? In my opinion, emphatically 
no! Every news-theatre will, as a mat- 
ter of course, have to have its television 
equipment, on which will be shown 
every important happening, both while 
it is taking place and, probably, for 
the benefit of subsequent audiences, a 
recording of the event also transmitted 
from the television station, but cut and 
edited like a newsreel. 

• The Projectionist's Viewpoint 

But probably there will be only one 
event a month of sufficient importance 
to justify depriving ordinary kinema 
audiences of their film program. For 
all other events, and for all those family 
theatres which are never likely to be 

Postpone Exam. Q. &. A. Series 

Publication of the projectionist ex- 
amination questions, and answers there- 
to, as offered by the Province of 
Ontario, Canada, which began in I. P. 
last month, has been postponed for 
sixty days in deference to the wishes of 
several projectionist organizations who 
have long sought just such a group of 
questions for their own uses. I. P. is 
glad to accede to these requests for the 
indicated period of time. — Ed. 

equipped with television, the newsreel 
will maintain its hold. 

What does television mean to the pro- 
jectionist? As far as I can see, once 
the equipment is installed and tuned, 
nothing more than working his own 
radio set. Naturally, in the early stages 
television engineers will be in attend- 
ance (a hint to those sound service en- 
gineers who have been displaced in 
recent months), but there seems nothing 
more in the equipment to necessitate 
any more attention that the projectionist 
is capable of. 

• Interference Serious Problem 

The one thing that does seem likely 
to cause trouble is interference. Some- near Marble Arch is a diathermy 
plant; eighteen months ago, when Sco- 
phony gave a demonstration in British 
Industries House, it caused trouble, and 
the same trouble was experienced in 
tests of the Baird equipment, causing 
"snowstorms" over the screen. Fortun- 
ately there was no trace of it during the 
actual performance. There .seems to 
be no cure for such interference except 
at the actual source. 

Most gratifying of all is the fact that 
this country has firmly established its 
lead in every branch of television. In 
America, progress has been held up 
by commercial factors, chief of which 
is the vicious circle, that without ad- 
vertisers to sponsor them, programs can- 
not be transmitted; without programs, 
receivers cannot be sold; and without 
receivers, sponsors cannot be obtained. 
From Germany, too, we have recently 
heard little of what appeared to be 
promising early progress. 

Better Magnet Wire Is Offered 
by General Electric Co. 

Eliminating the need for space-consum- 
ing protective coatings in many instances, 
Formex wire, a new and superior magnet 
announced by General Electric recently, is 
insulated with a synthetic resin which is 
tougher and more flexible than the con- 
ventional enamel coatings The new resin 
is of the polyvinyl acetal type, while or- 
dinary enamel coatings are composed of 
drying-oil resins. Since Formex wire re- 
quires less space for insulation and protec- 
tion, it gives the designer new opportunities 
to reduce the size of many products. 

Further, electrical properties are as good 
as those of ordinary enameled wires, and 
tests show that Formex is considerably 
higher in resistance to abrasion and to the 
common treating solvents. When severely 
twisted and then subjected to a tempera- 
ture of 125 C. for one hour, ordinary 
enameled wire cracks but Formex wire is 
not affected. It withstands the operations 
of winding, assembly, and varnish impreg- 
nation much better than commercially avail- 
able enameled wire. It can be used to ad- 
vantage in nearly all applications where 
enameled wire has been used, and in addi- 
tion it can be utilized in many applications 
to replace enamel-cotton, enamel-paper, or 
other fabric-covered wires where formerly a 
protective wrapping was necessary. 



Changeover Signal Devices 



GETTING around various pro- 
jection rooms, one cannot help 
being impressed by the many 
methods used to overcome the possi- 
bility of missing cue dots on the pro- 
jected picture. Let us first review 
briefly the Academy specifications for 
35 mm. prints: 

"Motor Cue shall be circular opaque 
marks with transparent outline printed 
from the negative which has had four 
consecutive frames punched with a 
serrated edge die .094 inch in diam- 
eter. The center of these holes is to 
be halfway between the top and sec- 
ond sprocket holes .281 inch from the 
right-hand edge of the film with heads 
up and emulsion toward the observer. 
Following the four frames containing 
the circular opaque marks there shall 
be 10 feet, (a total of 172 frames) 12 
frames to the beginning of the change- 
over cue. 

"Changeover Cue: Four frames con- 
taining circular opaque marks, 
punched similarly to and of the same 
dimension and position on the frame 
as the motor cue. Following the 
changeover cue marks there shall be 
18 frames to the beginning of the run- 
out trailer." 

Up to the time that the S. R. P. was 
adopted as the universal standard, the 
methods used to cue the picture included 
the following: Placing tinfoil around 
the edge of the film; scraping lines or 
crosses on the emulsion; splice that 
caused click through sound system; 
painting film edge with metallic paint 
to close an electrical circuit; pencil 
marks that were later removed; coin or 
metal placed in film near end of the 
reel; and leaving magazine door open 
to reveal amount of film still on the 
reel. Some of these things still are 
being done. 

• Sound Complicates Problem 

With the advent of sound pictures it 
is more than ever necessary to make 
perfect changeovers in order to prevent 
marring speech intelligibility and con- 
tinuity. Blank screens or the showing 
of the runout trailer are rather the ex- 
ception than the rule at present. Aud- 
iences paying the lowest admission 
prices will not tolerate this sort of 
showmanship, as is evidenced by the 
clamor set up when there is an inter- 
ruption of the sound or picture for even 
a few seconds. Good projection requires 
that someone be at the viewing porthole 
continuously to observe the picture. This 
is more than ever necessary since the 
introduction of Suprex arcs, which are 
highly sensitive in their operation and 

often require adjustment to maintain 
picture quality on the screen. 

Many things occur to take the pro- 
jectionist away from his regularly as- 
signed duties. Usually he is able to 
effect temporary repairs of sound or pro- 
jection equipment trouble before the 
audience voices its displeasure. On 
other occasions, and particularly while 
engaged in making repairs, many pro- 
jectionists have appreciated the need for 
something that would signal the ap- 
proach of reel-end cue dots and also 
provide a signal indicating when it is 
time to strike arc for following reel. 

During recent years many efforts have 
been made by inventive individuals to 
develop something to solve this problem. 
Some of these devices are electrically 
operated; others function mechanically. 
Some are quite simple to install and 
operate; while others are complicated 
and therefore defeat the purpose for 
which they were designed. 

It should prove interesting to describe 
briefly some of the devices, each of 
which will be designated by a letter. 

P. A. McGuire Honored By 
SMPE Projection Group 

Following is the 
resolution passed 
unanimously, in- 
scribed on a scroll 
and signed by the 
members of the 
Projection Practice 
Committee of the 
S.M.P.E. upon the 
occasion recently of 
Mr. P. A. Mc- 
Guire's resignation 
from the Commit- 
tee due to press of 
other activities: 

A. McGuire was 
actively instrumental in the formation of 
the Projection Practice Committee of the 
Society, and 

"WHEREAS, he has vigorously and help- 
fully contributed to the work of the Com- 
mittee through the intervening years and, 
by his thoughtful comments and friendly 
attitude, has won the respect and personal 
esteem of the Committee's membership, and 
"WHEREAS, he has found it necessary 
to discontinue his active participation in 
the work of the Committee, 
"RESOLVED, That the membership of 
the Committee hereby express their deep 
regret at his resignation from the Com- 
mittee: that they cordially extend to him 
an invitation to attend the meetings of the 
Committee whenever he may so desire: and 
that they convey to him their sincere good 
wishes for his continued success and future 
health and happiness." 

P. A. McGuire 

A. Light-Sensitive Device. A light 
source and a focusing and an adjusting 
device are contained in a case which 
is attached to the upper magazine. A 
light sensitive cell receives the beam of 
light as directed from the upper case. 
When the reel of film has been reduced 
to a predetermined length, the beam of 
light is no longer interrupted but passes 
to the cell, which action operates either 
lights or a bell signal. Thickness of the 
film, splices, the diameter of the reel 
hubs and other considerations make it 
necessary to change the setting on such 
a device for almost every reel of film. 

B. Photoelectric cell method of elim- 
inating visual cues and manual change- 
overs. The optical assembly collects 
light from the exciting lamp and pro- 
jects a line of light onto the film. The 
p.-e. cell is coupled to the amplifier in 
the usual way. Current fluctuations 
cause a voltage drop across a resistor, 
through a coupling condenser to the 
grid of the amplified tube. The output 
of the latter is matched to a frequency 
recorded on the film through a tuned 
relay of a momentary-contact type which 
closes a circuit to an interlocking relay. 
This closes a circuit to a motor which 
is geared to a revolving drum in such a 
manner as to cause the drum to revolve 
slowly at a predetermined speed. The 
drum is equipped for closing various 
circuits at predetermined intervals of 
time. The revolving drum closes the 
circuit of a bell or other signal which 
indicates that the reel is nearing its end 
and it is time to strike the other arc. 

Following this the projector motor 
circuit is closed by means of a switching 
arrangement. Operation of relays for 
control of douser and sound then occurs. 
The sound control is of the momentary- 
contact type which functions to close the 
ciixuit of the opposite coil, thus cutting 
out sound from the other machine. The 
outgoing projector is controlled maually, 
as the drum does not provide for this 

This system would undoubtedly re- 
move the cause of many complaints 
anent indistinct or missing cue dots; 
hut its multiplicity of circuits and con- 
nections make extremely doubtful its 
adoption for smaller theatres. 

C. Cue clips on film reels. A side- 
plate is used to mount the clips, which 
are set when the film is rewound at a 
predetermined point. As the film un- 
winds each clip is released at the proper 
time by means of plunger shafts within 
the spindle which operate mercury 
switches within the top magazine switch 
housing. The assembly is mounted on 
each projector top magazine hangar 
castings with two set screws. 

At a predetermined point the cue is 
{Continued on page 25) 

MARCH 1939 


New Forms for Electrical Data 

THE highly condensed information 
included in electrical diagrams and 
data sheets, always invaluable, has 
recently been presented in new forms. 
The complexity of modern equipments 
has led to the development of improved 
styles of abbreviated presentation 
through which, it is expected, drawings 
will be easier to read. A review of the 
entire subject is timely. 

Diagrams and data sheets have always 
been planned to convey at least five 
separate categories of useful informa- 
tion. They indicate: (a) the component 
parts of an apparatus; (b) the electrical 
ratings or values of each of those parts, 
as, for example, the capacitance of a 
condenser; (c) their schematic, or elec- 
trical, relationship, as where a diagram 
shows that a certain transformer prim- 
ary constitutes the plate load of a cer- 
tain tube; (d) the physical location of 
the parts in the apparatus assembly; 
and (e) the physical locations and ter- 
minations of the connecting wiring. 


The value of this data in trouble- 
shooting, repair and replacement work 
is obvious; there remains a practical 
question as to the methods of presenta- 
tion that will convey it most efficiently. 
Four common methods are used, none 
sufficient in itself. They are: the sche- 
matic diagram, the wiring diagram, the 
tabulation, and the physical marking 
of the actual apparatus. 

Each of these methods is subject to 
periodic changes of detail intended to 
improve its efficiency, reduce its cost, 
or both; each therefore may be en- 
countered in varying forms in which 
the information embodied may not be 
immediately recognized. The simplest 
presentation, and the one so far least 
subject to change, is the familiar sche- 
matic drawing. 


A simple schematic is given at the 
bottom left of Fig. 1. It has only one 
unusual feature, namely, the somewhat 
large number of rectifier tubes here used 
in parallel. Most readers of I. P. will 
be able to understand the diagram at a 
glance; however, it may be traced briefly 
here for comparison with another dia- 
gram of the same apparatus also in- 
cluded in Fig. 1. 

The schematic is that of a rectifier 
receiving a. c. from a power line and 
delivering 220 volts d. c. The input 
is at the left, through the fuse F-l and 
the switch S-l. The power transformer 
primary is tapped for 105, 115 or 125 
volts, allowing the same apparatus to 
be used efficiently in different communi- 

The lower transformer secondary 
heats the filaments of the four rectifier 
tubes. The upper secondary supplies 
the plates. The action can be consid- 
ered with reference to VT-1 alone, since 
the other three tubes are in parallel 







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• 931 



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• -106 

5Z3 vacuum tube 

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hi ems dihghhm t schcimtic 


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to VT-1 and serve only to add to the 
total rectified amperage. 

Electrons will flow from the filament 
of VT-1 to whichever of its two plates 
is positive at any given moment, thence 
(continuing to trace from negative to 
positive) through the transformer wind- 
ing to the center tap of the upper sec- 
ondary. Then to the right through the 
negative output line, through the ex- 
ternal load, in at the positive output 
line and left through the choke coil, 
completing the circuit by returning to 
VT-1 filament. 

The electron stream in the output 
circuit cannot reverse its direction of 
flow, since the rectifier tube is a one-way 
valve; hence, a. c. has been converted 
to d. c. 

The diagram just considered gives, 
however, only one class of information. 
It reveals the electrical relationship of 
the different components and the elec- 
trical functioning of the circuit. It does 
not even mention what type of tube must 
be used for replacement. It does not 
give the rating of the fuse, F-l. There 
are no ratings for the choke coil or the 
condenser to guide replacement when 
required; and though the output volt- 
age is mentioned, the secondary voltages 
of the transformer (knowledge that 
might be useful in checking trouble) 
have not been included. 

Further, there is no indication of the 
physical placement of the components, 
which would assist in identifying them 
in the actual apparatus, and no guide 
to the physical placement or color cod- 
ing (if any) of the connecting wires. 
In short, a great deal of data that might 
prove extremely valuable in an emer- 
gency is omitted. 

Some schematics give more detail. 
Very often they designate tube types, 
and sometimes carry legends indicating 
the ratings of other parts. Some few 
show the color coding of wires. But 
physical replacement of parts, or of wir- 
ing, is almost never included in any 
but the very simplest schematics. It 
cannot be included without sacrifice of 
that electrical simplicity which is the 
schematic's chief value. 

• Wiring Diagrams 

The greater bulk of Fig. 1 is occupied 
with the wiring diagram of the same 
apparatus, in which can be found much 
of the information not included in the 
schematic. Here the component parts 
are outlined in their proper shapes and 
proportionate sizes, and located exactly 
as in the apparatus itself. They are 
identified with their counterparts of the 
schematic by means of abbreviated des- 

L-l, the filter choke, is drawn at the 
bottom right; C-l the condenser at bot- 
tom center, and T-l the power trans- 

former at center left. The four tube 
sockets are grouped at upper left; the 
fuse receptacle occupies the upper right- 
hand corner; while the switch, and the 
input and output terminal strips are 
shown at the extreme top of the draw- 

The diagram also shows the exact 
physical course and location of every 
connecting wire, and the wire color. It 
identifies the locations of the individual 
transformer terminals on the trans- 
former block, and shows, further, that 
the plate secondary center-tap is 
grounded to the chassis, a fact that 
might be very important in trouble- 
shooting but is not shown on the sche- 
matic. The filament secondary voltage 
is also given (5 volts), but the plate 
secondary voltage is not stated. 

Another interesting fact is that the 
tube sockets are drawn with two large- 
diameter terminals and two of smaller 
diameter. As a matter of fact, the former 
are the filament terminals, but Fig. 1 
does not clearly indicate this. For that 
information those who are not aware 
of the common practice of making the 
filament prongs of a tube thicker than 
the other prongs must go to a book or 
chart of tube data. 

• Tabulations 

Most of the apparatus of the wiring 
drawing is contained within the dashed 
rectangle which, the legend indicates, 
shows the bottom view of the chassis; 
but the terminal strips and switch S-l 
are outside that rectangle, therefore 
they cannot be found by turning the 
rectifier upside down. Those items must 
be sought at the front and sides of the 

To the right of Fig. 1 is a tabulation 
containing still other data. Here will 
be found the rectifier tube designations, 
the rating of the fuse, and that of the 
condenser. For replacement purposes, 
part numbers are given which facilitate 
the placement of orders therefor. The 
inclusion of this data in a separate tab- 
ulation avoids cluttering up the draw- 


ing proper, thus making the wiring de- 
tail easier to follow and at the same 
time enabling the printing of informa- 
tion in larger type. 

Figure 2 is another form of tabula- 
tion, relating to apparatus of earlier 
design in which actual wiring informa- 
tion is given in a listing rather than 
in a drawing. The apparatus covered 
by Fig. 2 is a terminal block housed 
in a connection box. The only informa- 
tion required relates what pair of wires 
go to which set of terminals. 

Figure 2 gives this data as efficiently 
as a drawing could. The central column 
numbers the terminal pairs, from 1 to 
20. Refer to the top line of data. Ter- 
minals 1 (read from left to right) re- 
ceive on the one hand a pair of No. 18 
wires in a lead sheath (D. LD. = two 
wires in lead) from the No. D 88422 
control cabinet; from Terminals 38 and 
40 of that cabinet. 

At Terminals 1 of this connection 
strip those wires are joined to the leads 
to Horn No. 1, those leads having their 
termination at the B-box connection 
strip, and consisting of two No. 14 
braided rubber covered wires. A dia- 
gram could not, in this instance, give 
clearer information, and tabulation is 
more compact and easier and quicker to 

• Incidental Notes 

Both tabulations and diagrams often 
carry incidental notes of high value, not 
to be neglected. For example, Fig. 2 
notes that Terminal pair 20 are 
grounded to the connection box. This 
note is at the upper right in small type. 
Two other notes at right center give 
the drawing numbers of diagrams which 
convey in drawing form the same in- 
formation as the tabulation. 

It will be seen that both Figs. 1 and 
2 carry at their extreme right a column 
for additional notes. In this particular 
example that column is not used except 
for the date of issue. However, suppose 
that the circuit or parts constants of 
Fig. 1 are modified in the course of 
time, perhaps to effect some minor im- 








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TERM 38'40 





18 OLD 




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MARCH 1939 


provement. That modification will be 
indicated in the right-hand notes column. 
In the case of a drawing obtained 
from a manufacturer after shipment of 
the apparatus, the right-hand note col- 
umn should always be consulted to de- 
termine if any changes have been made 
in the drawing to which the apparatus, 
being of older model, does not conform. 
If this point is not checked, the draw- 
ing may prove very seriously mislead- 
• Physical Markings 

A wiring diagram such as that of 
Fig. 1 is very often supplemented by 
reproduction of the same or equivalent 
markings on the apparatus itself. Thus, 
transformer terminal numbers may be 
stamped on the transformer terminal 
strip. Polarities are usually indicated. 
Resistors and condensers may carry 
their ratings in plain type or in color 
code; both also may be marked with 
their designation in the particular unit 
in question, as R-l, C-l, etc. 

In some equipments individual parts 
carry, in addition to all this information, 
their parts numbers corresponding to 
those given in the tabulation of Fig. 1. 
These markings, however, often are ob- 
scured by heat and dust, and may after 
some years become illegible; thus the 
wiring diagram becomes proportionately 
more valuable in the case of older ap- 

Details of drawing and tabulation 

methods change constantly, but in many 
cases the new procedure can be inter- 
preted easily enough on a common- 
sense basis. Thus, in the schematic of 
Fig. 1, VT stands for vacuum tube — 
a familiar abbreviation long used. VS 
in the wiring drawing is relatively a 
new abbreviation, but obviously it means 
"vacuum (tube) socket". The fuse is 
designated as F in the schematic, and 
as FS in the wiring drawing. Small 
variations of this type are very common. 
Similarly, in Fig. 1 the tube plates are 
drawn conventionally as rectangles. In 
the schematic of Fig. 3 they are given 
the less usual form of triangles. 

• New Diagram Form 

Figure 3 also incorporates a very new 
form of wiring diagram and one that 
promises to become increasingly com- 
mon in the future. 

Refer to Fig. 1. Just above the con- 
denser, C-l, there is a short stretch 
wherein seven wires run parallel to each 
other, being a trifle hard to follow. 
The man tracing some one of those 
seven wires may become so far confused 
as to transfer his eye or pencil point 
to the wrong line. There is compara- 
tively little danger of this in Fig. 1, 
because the wiring is scanty and simple. 
But everyone has seen drawings in 
which the complexity of detail is so 
great that every line has to be traced 
two or three times to insure accuracy. 


Figure 3 is a wiring diagram that 
eliminates this risk at some small sac- 
rifice in the amount of information 
given. It can be read far more easily 
and quickly. In that diagram the parts 
are shown in their proper physical place- 
ment, just as in Fig. 1. The terminals 
are correctly shown and marked. Wires 
are all shown and color-coded. But the 
paths followed by the wiring are not 

Instead, the connections are indicated 
by printed information. Refer to TS-1, 
top left of the drawing, and to the left 
terminal of that strip, marked "DC". 
To that is connected the stub of a white 
wire, labelled "TS-3DC". Now refer 
to TS-3, extreme left center just below 
TS-1. At the left of TS-3, the second 
line from the top is a white wire la- 
belled "TS-1DC". This is obviously the 
ether end of the same line, which con- 
nects the DC terminal of TS-3 with the 
d. c. terminal of TS-1. The only thing 
not shown is the actual path of the con- 

The same method is followed through- 
out. Thus, refer to L-l, the choke coil 
just below TS-3. A stub wire (not color- 
coded) springs from the left of that 
coil and is marked TS-3. Referring to 
that terminal strip we see that a wire 
from L-l comes in at its upper right- 
hand terminal. 

Or refer to the schematic at the bot- 
tom of the drawing. It will be seen 

WD- 123 

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TS 2 

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TS 4 

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that there are two chokes, L-l and L-2, 
and that the jumper between them con- 
nects to one side of C-l. Now, looking 
up at the wiring drawing, it will be 
seen that the two chokes, L-l and L-2, 
each carry a stub of wire labelled TS-4. 
At TS-4, directly above, these two stubs 
are shown coming into the second ter- 
minal from the top, and from that ter- 
minal a wire runs left to one side of 
condenser C-l. 

The wiring drawing of Fig. 3, 
although occupying relatively bttle 
space, is entirely clear and easy to fol- 
low. If all the connections were drawn 
in as in Fig. 1, Fig. 3 would have to 
be made considerably larger or it would 
he too crowded for quick, practical use. 
The new method it employs bids to be- 
come universal for all complex circuits 
in the not distant future. 

• Schematic of Fig. 3 

The wiring diagram of Fig. 3 is of 
course further clarified by reference to 
the schematic. This deals with an ex- 
citer lamp supply circuit equipped with 
triple provisions. First, there is a rec- 
tifier to provide the lamp with direct 
current. However, a switch makes it 
possible to substitute 9.5 volts of a. c. 
temporarily to keep the show going in 
case of rectifier failure. Finally, there 
is a "pre-heating" circuit delivering 2 
volts a. c. to the exciter lamp not in use. 
This provides faster changeover, the pre- 
heated lamp coming up to full illumin- 
ation more quickly; and also permits 
the lamp to be used for some testing 
purposes between reels. 

Alternating current enters at the 
right, and one branch continues left 
through S-l and F-l, down through the 
primary of T-l, and back right- 
ward to the other side of the power 
line. T-l has two secondaries, in series. 
The full-voltage emergency a. c. supply 
may be traced left from the bottom sec- 
ondary terminal through R-l and out 
through the emergency switch to the 
output terminal labelled DC; back in 
at the common and right to the series 
tap on the transformer secondary. 

The common also connects through 
the exciter lamp with the "pre-heat" 
output terminal, marked "AC". Switch- 
ing these outputs is a function of the 
changeover switch, and those facilities 
are not shown in this diagram. 

Returning to the a. c. input at the 
extreme right, a branch may be traced 
downward from the right side of F-l 
and left to the emergency switch. When 
this is down, for rectifier operation, the 
same line returns to the right to one 
side of T-2 primary, through that wind- 
ing and up to the AC input common. 

There are three secondaries, of which 
two light the filaments of the rectifier 
tubes, VT-2 and VT-3. One filament 

Television, Sound Recording Papers To 

Feature S. M. P. E. Program 

DISCUSSIONS of television studio ture work are carried out, property and 

technique and lighting, a new mag- wardrobe departments, and the labora- 

netic recorder and its adaptations, a tories. 

"time telescope," and a review of for- The following table lists the railroad 

eign film markets are a few of the fares and Pullman charges from various 

widely varied subjects to be presented cities to Hollywood, 

at the Spring convention of the Society r „ ,, 

of Motion Picture Engineers at Holly- r . t , * a , re . , Pullman 

wood, April 17 to 21, inclusive. Head- ^gT (r 2¥2?£ P) fe^ 

quarters will be at the Roosevelt Hotel. Washington . . . f 132.20 $22.35 

The television symposium includes ^ , g0 90.30 16.55 

papers by representatives of RCA, NBC, £°f °\ \fi^ ?3.65 

CBS, Dumont, Don Lee, and a report " etro * ; {^^ 19-20 

by Dr. A. N. Goldsmith, chairman of £ ew , Y ° rk ■"• ^9.75 22.85 

the SMPE Television Committee. Rochester 124.05 20.50 

An important paper on a direct posi- ™ e ™ 1 ™ d , ™™ JJ20 

tive system of sound recording, by G. L. ?/ t la K delp , hia " ' ' ^.50 22.35 

Dimmick and A. C. Blaney of RCA, Plttsbur S h ■■■■ H™ 19.70 

will be presented, as will a paper on The usual equipment display will be 

RCA aluminate developers, by J. R. held at Convention headquarters. Pros- 

Alburger. pective exhibitors should contact the 

"The Polyrhetor — a 150-Channel Film Society immediately. The social side of 

Reproducer" will be presented by G. T. the Convention will include the usual 

Stanton, of Erpi, and F. R. Marion and Society banquet, an elaborate program 

D. V. Water, of W.E., at a demonstra- for the entertainment of the ladies, 

tion. A discussion of lens making in passes to Hollywood theatres, and the 

America will be presented by W. B. usual sports privileges. Many members 

Rayton, of the Bausch and Lomb Optical plan to include a visit to the Golden 

Co. A. A. Mercey, of the United States Gate Exposition in San Francisco on 

Film Service of the National Emergency their itineraries. 

Council, will present a paper on the 

new frontiers for the documentary film. ANOTHER VICTIM OF OKLAHOMA'S 

A light-weight sound recording system "NON-HAZARDOUS" OCCUPATION 

will be discussed in a paper by r. L. TT „. T t , ,, „_ .. ... 

u i? /-■ tit j x ij j r> r> Hollis Haskell, zz-year-old proiectiomst, 

Hopper, L. L. Menderfeld and R. R. „ ( „. „ , ' , / c y ,i J . ' 

c -ii x 1? was fatally burned by a fire that swept 

?? ™ °A i P1- r , • i t. through the Strand Theatre, Phoenix, N. Y., 

C. M. Mugler, of the Acoustical En- recently, and also burned severely a high- 
gineering Co. will present a paper on school student who was in the room at the 
"Controlled Sound Reflection." A dis- time. The latter jumped from a window 
cussion of a new mobile film recording to the floor 10 feet below, but later re- 
system will be presented by C. L. turned to attempt a rescue of his projec- 
Lootens, of Republic Production, and tl0nist f " end -. Haskell succumbed to sec- 
B. Kreuzer, of RCA. ? nd " and ^-degree burns withm four 
' hours alter the fare. He never recovered 
# Studio Visits Arranged consciousness after the first blast of flame 

Visits to the Paramount and Warner and g ases swe P l throu g h the Paction room, 

studios will be highlights of the con- Oklahoma State Supreme Court only re- 

vention. These tours will include cently a ffi rme d a n earlier decision holding 

visits to the projection background projection work to be a "non-hazardous" 

shooting stages, the sound and dubbing occupation and one that does not entitle 

departments, production stages, the projectionists to compensation in the event 

stages where special effects and minia- of injury by fire or otherwise while han- 
dling film. 

or the other will at any given moment EXCHANGE SAFETY RECO RD 

be negative with reference to its plate Whh ^ ^.^ ^ ^ ^ 
and the electron stream can be traced tion picture fflm bdng handled daily in the 
from that filament to the plate, thence exchanges owned by members of the Mo- 
left and up to the common output, tion Picture Producers and Distributors of 

through the exciter and in through the Amer 1 T fil (H ? ys ° &C H' theI ? W . be ™ 

. " • t i ii only 11 turn fares in these exchanges in the 

d. c. output terminal, down, through 13 . year period from 1926 t0 ig3Q Aggre . 

the left blade of S-2, to the right gate money damage was only $4,477.50. 

through R-2, through the ballast lamp 

VT-1, through the filter chokes to the CANADA BARS 35 MM. PORTABLES 

center tap of T-2 secondary, and thence Standard rental agreement of the Film 

,, i .i . xn.™ t „„„;„ Boards of Trade in Canada has stopped the 

through the jumper to filament again. r ^i ,. „ oo , Q r ■ . . v n u 

" ii i_ turther use ot ao mm. pictures in halls by 

The reader can readily trace as much prohibiting the booking of standard films 

or as little of this wiring as he has except for theatres having permanently in- 

need for at any time through the ab- stalled projection machines and sound sys- 

, . , . ^ l x *u x terns, lhis means the termination of stand- 

breviated wire stubs of the aforemen- ard fflm exhibition with portable proje ction 

tioned new style diagram. equipment. 

MARCH 1939 



Sixth Subscription Contest Diagram 

PARTICIPANTS in I. P.'s Diagram 
Contest continue to amaze by their 
utter lack of consistency. From a rec- 
ord high of 28 successful entries on the 
January issue circuit the boys slumped 
so badly as to provide only two win- 
ners, out of a total of more than 80 
contestants, on the circuit offered in 
the February issue. The only winners 
this month are C. E. Mervine of Potts- 
ville, Penna., and Francis L. Hill, of St. 
Petersburg, Fla. — both of whom, in- 
cidentally, are officials of I. A. local 

Here is the lineup of the errors ap- 
pearing in the February diagram (Fig. 

1. Jumper added from center tap of 
F secondary to the. center tap of H 

2. Ground removed on lower end 
microphone transformer secondary. 

3. Cathode bias resistor removed on 
first tube. 

4. Jumper removed between .015- 
and .0005-mfd. condensers. 

5. Jumper added between tops of 
dual Vk-mfd. condensers in first tube 
plate and screen circuits. 

6. Jumper added (without connec- 
tion dots) from the grid of lower out- 
put tube to the plate line. 

Now, just what should have proven 
so very tough about this diagram it is 

difficult to say. The circuit is that of 
a De Vry amplifier for 35 mm. repro- 
duction, very few of which have been 
used in the theatre field. It was intro- 
duced about five years ago, which means 
that it does not reflect the use of such 
advanced engineering as might offer 
much trouble to projectionists who know 
their circuits. 

• Grid Connections Mislead 

There would undoubtedly have been 
many more winners were it not for the 
fact that most contestants were misled 
by the grid connections of the second 
tube, the general assumption being that 
those connections had been changed 
from the conventional grid arrange- 
ments. The use of positive control grid 
and connection of signal to the screen 
grid, as shown in Fig. 1, is sometimes 
resorted to in order to get higher gain. 

Contestants seem to be about equally 
divided on the question of whether the 
incorrect diagram should be reprinted 
and the errors therein summarized, or 
the correct diagram should be repro- 
duced. The latter course would have 
the very definite advantage of providing 
I. P. readers with a series of diagrams 
relating to many and diverse types of 
amplifier circuits. 

The current Contest diagram (Fig. 2) 
offers an entirely conventional circuit. 
As usual, the more important parts of 
the circuit have been redrawn, thus mak- 
ing futile any attempt to check the 
errors through possible faulty inking. 
Only subscribers to I. P. are eligible 
for the award, which continues to be a 
free subscription to I. P. for one year. 

All replies must reach I. P. not later 
than April 20 in order to receive con- 
sideration. It is not necessary to en- 
close a copy of the diagram, either the 
original or a copy thereof. A list of 
the errors found will suffice. 




Addendum to Cooperative Work by 
Projectionist and Serviceman 

More Gleanings from Altec Service Corp. Files Anent Field Teamwork 

CRIES of: "Encore!" Well, I asked 
for it, and I got it! Last month, I 
wrote an article made out of "true 
life stories" I dug up out of the Altec 
files, — true life stories about how the 
team of projectionist plus serviceman 
could like a problem in a spirit of hearty 
cooperation, when neither one could lick 
it alone half so easily. 

Then, at the tail-end of the story I 
said "Would you like to hear more 
stories along this line?" and gosh! your 
letters and comments told me in no un- 
certain terms to "do an Oliver Twist" 
— and go back to the Altec files for an- 
other helping. So here's lookin' at ya! 

• He Unearthed — A Crank! 

At 6:56 P.M. on a recent Tuesday 
afternoon, the Colonial Theatre at 
Phoenixville, Pa., put in a call for the 
Altec inspector. The motor driving No. 
2 machine wouldn't "pick up" to nor- 
mal speed. Because it wasn't prac- 
ticable for the inspector to talk to the 
projectionist, he couldn't learn any 
more details or offer possible methods 
of correction over the 'phone. So he 
told the manager he would start imme- 
diately for the theatre. 

Arriving at the theatre, the inspector 
thought to himself : "Well the show'll 
be running on one machine, with the 
historical 'One Minute Please' being 
flashed on the screen while the single 
good machine is being threaded for the 
next reel!" 

Imagine his surprise when, on arriv- 
ing in the projection room, he found 
the show operating normally on two ma- 
chines! How come? The reason for 
this unexpected serenity of affairs was 

During the time the inspector was 
racing to the theatre, the projectionist 
put on his thinking cap in a big way. 
He reasoned like this: "If the motor 
hasn't enough power to bring the ma- 
chine up to normal speed, how could / 
get the motor up to normal speed?" 

Now I'll detour just a second for the 
benefit of you young fellows who don't 
remember the old days of the motion 
pictures — yeah, they were called 
"flickers" then, and they used acetylene 
lamps and, so help me Hannah, a hand 
crank to operate the projector! 

Well (shades of the old days when 

MARCH 1939 


they still put a buggy-whip socket on 
the old automobiles ! ) it's a fact that 
present-day projectors still are equipped 
with facilities for inserting an old- 
fashioned hand crank*. So our hero 
(the projectionist) has the following 
big-time brain-wave: 

"I remember seeing an old hand- 
crank somewhere around here!" He 
rummaged around among a lot of as- 
sorted junk that had just never been 
thrown out. Lo and behold — he found 
the crank! He stuck the crank in the 
place provided for it in the projector, 
cranked like hell and brought the ma- 
chine up to normal speed. 

Then came the big surprise. He fig- 
ured he would have to continue 
cranking the machine, but was de- 
lighted to find that once the machine 
was boosted up to normal speed, the 
motor was able to carry on and hold 
to the normal pace. So, each time it 
was necessary to run the No. 2 machine, 

*ED.'s NOTE: This ingenious method of keep- 
ing the show going is possibly only with cur- 
rent Regular and Super-Simplex projectors; and 
forthcoming models of the latter will not permit 
this procedure. It is entirely possible to utilize 
this method because the motor, once up to 
speed, ran along on its own. 

Micro-Photographs of Projector 
Parts To Appear in I. P. 

BEGINNING with the next issue, 
I. P. in cooperation with Inter- 
national Projector Corp., will pub- 
lish a series of micro-photographs of 
various components of motion pic- 
ture projectors, with special em- 
phasis upon those defects which 
contribute materially to faulty oper- 
ation. The pictures will be shot on 
a Zeiss toolmaker's microscope hav- 
ing a photographic attachment 
permitting an enlargement of 42 

Projectionists in the field who 
desire to submit particularly glaring 
examples of worn or faulty projec- 
tor components — sprockets, gears, 
etc. — are cordially invited to do so. 
Because of space limitations and 
other considerations, I. P. cannot 
guarantee to reproduce every such 
part submitted, although every effort 
will be made to make the series of 
pictures as inclusive as possible. 

the projectionist brought the motor up 
to running speed with a half-dozen revo- 
lutions of the crank — and the show con- 
tinued uninterruptedly, the audience not 
being aware of anything being different. 

So you see what I mean when I said 
"Imagine the Altec inspector's sur- 
prise!" Well, there's no substitute for 
experience and mental alertness and the 
projectionist thought of using a hand- 
crank — and then dug it up out of the 
mothballs ! 

The inspector traced the trouble in 
the motor to a defective transformer in 
the 708-A motor control cabinet. A 
nearby Altec emergency stock point was 
contacted, and a replacement for the 
transformer was shipped to the theatre 

• A 'Short' — Not A Crank 

Here's another case of exactly the 
same trouble. The drive motor just 
wouldn't pick up to normal speed. So 
the Rialto Theatre at Tonkawa, Okla- 
homa put in a call for Altec. But in 
the meantime, the projectionist asked 
himself, must my show limp along on 
one machine for several reels? Not 
liking the idea worth a damn, the pro- 
jectionist decided to go on a still-hunt 
on his own. 

When the motor first started to act 
up, he quickly checked over the motor 
proper. He couldn't find anything 
wrong. So where do we go from here? 
Answer: obviously the 708-A motor con- 
trol cabinet. 

In looking over the various com- 
ponents of that intricate piece of ap- 
paratus, he reasoned that the motor 
would come up to normal speed all by 
itself — if he momentarily short-circuited 
resistors R-6 and R-7! As soon as the 
motor came up to its standard 1200 
r.p.m., he found he could remove the 
short-circuit across R-6 and R-7 and the 
motor would continue merrily to turn 
the machine at its standard speed! 

So he kept the show going on both 
machines this way, until the Altec man 
got to the theatre and cleared the 

Here's the technical dope on what 
the projectionist did when he short- 
circuited resistors R-6 and R-7: These 
two resistors are in the grid bias circuit 
(Continued on page 24) 


Ohm's Law and its Application 
to Some Projection Problems 

ELECTRICAL resistance plays so 
important a part in the daily work 
of the projectionist that a thor- 
oughly practical understanding of Ohm's 
Law is a fundamental requisite for his 
work. The algebraic forms: 
E E 

1=-- E=1R and R=— 
R, I 

are probably quite familiar to everyone. 
We can substitute values at hand for 
any two of the three quantities consid- 
ered and find the third; but does this 
imply that the real meaning and appli- 
cation are clear and that when con- 
fronted by a problem involving current 
volts and ohms the Law can be readily 
employed in its solution? 

The writer has had many years of ex- 
perience in the motion picture field. It 
has now been 24 years since the appear- 
ance of the Transverter, but we still re- 
ceive letters from projectionists which 
show plainly that they have missed the 
point of just what it all means. 

• Prime Considerations 

In any carbon arc, no matter of what 
kind, the main considerations are amount 
of current, voltage across the arc, and 
length of arc. These are all interde- 
pendent, yet if two of the three are fixed, 
it does not mean that the third will 
always assume a definite value. This 
is true largely because, while we have 
done nothing to change the apparent 
length, the flow of the arc may have 
assumed a new path with a different 

This apparent discrepancy seems to 
bedevil the Suprex arc more than some 
of the older types. Horizontal operation, 
together with the very special construc- 
tion and materials of the carbons, prob- 
ably explain this. Lengthening the arc 
increases the voltage across the arc or 
decreases the amperes, or does a little 
of each — usually, but not necessarily. 

Quite often when operating an arc on 
a ballast of fixed resistance and with a 
supplied voltage so steady that there 
was no discernable variation, the current 
is found to vary, sometimes abruptly 
and sometimes periodically, especially 
if the current strength is not suited to 
the size of carbon used. It is this con- 
dition that is mystifying and leads to 



a suspicion as to the infallibility of 
Ohm's Law. 

The Suprex arc today is operated 
either off a generating source of constant 
voltage with a ballast resistance, or off 
a source having what is known as a 
drooping characteristic, that is, as the 
demand for current increases the volt- 
age produced by the generating device 
decreases. With the drooping charac- 
teristic it is possible to operate without 
the use of ballast, but two arcs cannot 
be burned simultaneously from the same 
generating source. 

With the other plan, using a constant 
voltage source, this voltage is held some- 
what higher than that required for the 
arc, the difference being consumed in 
the ballast. In this manner two or more 
appliances can be used at one time, and 
the arc in each will burn independent 
of all the others. The Suprex arc is 
particularly adapted to this sort of op- 
eration because the ballast resistance 
required is small, being on the order 
of 6 to 10 volts in place of the 25 to 30 
usually employed with the higher volt- 
age arcs. 

Supposing, then, an arc is burning 
on a constant voltage source with a 
ballast in series. The voltmeter, if 
steady, will show that the generator out- 
put is constant. If the voltage should 
change, the voltmeter would tell how 


much, just when, and for how long. 
The ballast, adjusted with a certain 
position of the handle or with a certain 
combination of short-circuiting clips, 
has a very definite resistance, which 
means that with a given current in am- 
peres the voltage across the ballast can 
be only one definite thing. The one 
thing that cannot be controlled is the 
resistance of the arc itself. 

• Unwarranted Criticism 

All of which leads us to an important 

// ihe voltage remains constant as 
shown by the meter across the generat- 
ing source while the current is fluctuat- 
ing, the current source cannot be blamed 
for these fluctuations. 

Suspicion will next fall on the ballast. 
Herein is always present a possibility 
of poor or loose connections, which are 
really the only cause of rheostat trouble. 
To detect such trouble is not so easy, 
since the voltmeter across the rheostat 
or ballast will keep step with the fluc- 
tuations of amperes in the arc because 
our old friend Ohm's Law is in full 
force and 


// the resistance remains constant, as 
it should, and the current changes, the 


Multiple progressive 

Multiple selective 



voltage drop across the ballast will 
change up or down in proportion to the 
current change. 

One way of detecting rheostat trouble 
is to look for hot spots. The writer 
has found rheostat installations in which 
the series ribbon type is used, and where 
the resistance value is adjusted by the 
cutting out or in of clips on the front, 
where the clips had not been tightened 
and were so hot as to burn the hand. 

Another way of checking ballast is 
to put a voltmeter across its terminals 
and watch it in conjunction with an 
ammeter. If at any time a fluctuation 
of the voltmeter can be detected when 
the ammeter is steady, the trouble is def- 
initely located in the ballast. 

Ballast resistances, of both the series 
and the multiple type, are so constructed 
today that very fine gradations of cur- 
rent values are possible and usually no 
adjustment of the field regulator is re- 
quired. These finer gradations are ac- 
complished in both the series and the 
multiple types by using sections of var- 
ious resistance values and then arrang- 
ing that these are inserted selectively 
rather than progressively. 

To dig into this topic a little deeper: 
the multiple type of resistance generally 
consists of wire coils, cast grids or, in 
some cases, ribbon, the one end of each 
being attached to one rheostat lead, 
while the other ends are brought to 
either a series of contacts which are 
swept by an arm (Fig. 1) or to inde- 
pendent switches (Fig. 2) the arm or 
switch being then connected with the 
lead of the rheostat. 

If the arm be used, the sections of 
resistance can be cut out or in pro- 
gressively only. There is no choice. If 
the independent switches be used, the 
sections can be cut in or out selectively, 
any one being operable at will without 
disturbing the others. 

Similarly with the series type of re- 
sistance where all the sections carry the 
whole current, an arm (Fig. 3) can be 
arranged to cut the sections in or out 
progressively, or clips (Fig. 4) can be 


W\ft ] /wv\ 1 wvywv\ 

used to "'short out" any section select- 

As an illustration, suppose there are 
five sections of these which have values 
of 1, 2, 4, 8, and 16 ohms and all have 
the same current capacity, the total re- 
sistance series-type being 31 ohms. No. 
1 may be shorted (Fig. 4) leaving the 
resistance 30; No. 2 may be shorted, 
leaving a balance of 29; Nos. 1 and 2 
give 28; No. 4 gives 27; Nos. 1 and 4 
give 26; Nos. 2 and 4 give 25, and so 
on in 1-ohm steps down to a final value 
of 1 ohm. However, if all of these steps 
were made of the same value, approxi- 
mately 6 ohms each, we would be able 
to get only 30—, 24—, 18—, 12—, and 
6- ohm steps. 

In the multiple type the same plan 
brings the same results (Fig. 2). A 
shift in the position of the field regu- 
lator should no longer be necessary, 
except possibly in going from an aver- 
age to a very dense film. The temporary 
adjustment is possibly more easily ac- 
complished in this way. 

• Elements of Confusion 

There are always a number of un- 
looked for possibilities that tend to con- 
fuse one, and sometimes put unmerited 
blame on a unit of equipment. It is 
not unusual to have a steady generator 
voltage but an unsteady arc due to im- 
perfect contacts in the ballast rheostat 
or in the wiring. A recent case of this 
kind was blamed first on the generator, 
then on the rheostat, but the trouble 
was finally found in the wiring. The 
actual fault was hidden in the conduit 
imbedded in concrete where it could 
not readily be discovered, and it was lo- 
cated only after all combinations of 
lamps, wiring and ballast had been 
tested. The fault always accompanied 
the combination which included that 
particular part of the wiring which 
proved defective. This wiring had to 
be pulled and repaired. 

Frequently it is found that the clips 
on the series-type ballast now widely 
used were changed but not tightened. 
Heating and, in some cases, oxidation 

ensued with consequent fluctuation of 
the arc. 

Shortly after the introduction of the 
Suprex arc, where two lamps are burned 
alternately, and on changeover simul- 
taneously, oft" the same generator, each 
lamp with its ballast, complaints were 
made that on throwing in the second 
lamp the light on the first lamp would 
dip. Investigation showed that this 
statement was true. The voltmeter across 
the generator showed no drop with the 
burning of the second lamp; in fact 
sometimes an actual slight rise in volt- 
age would ensue indicating overcom- 

Further investigation showed that in 
most instances the distance from the 
projectors to the generator was rather 
long, and the wire, while in accordance 
with Underwriters' requirements, had 
enough resistance drop to account for 
the trouble. Probably the first thing 
to occur to most projectionists con- 
fronted by this condition would be to 
increase the size of the wire and its 
consequent carrying capacity so as to 
minimize this effect. 

A much better solution was worked 
out. By running two independent lines 
to the lamps the trouble was entirely 
eliminated; the amount of copper used 
was no more than in the original instal- 
lation. The line drop caused by the 
current in either lamp was then confined 
to that lamp, and this drop could then 
be considered a part of of the rheostat 
drop and had no distorting effect. 


Bill which has advanced to a third read- 
ing in N. Y. State Legislature, and affecting 
only N. Y. City, not only establishes a 
licensing system for projectionists and mini- 
mum training requirements for apprentices, 
but makes it a misdemeanor to employ, or 
permit to operate, an unlicensed man in 
any theatre or place of public admission 
where motion pictures are exhibited, with 
or without charge for admittance. 

Measure also asks employment of not less 
than two licensed projectionists where there 
is more than one projecting machine on 
the premises. 

Series progressive 

MARCH 1939 


Series selective 





ANEW type of background projec- 
tion apparatus has been developed 
using the Mitchell sound or eccentric 
movement identical with the one used 
in the latest cameras, except for some 
minor details. 

The principal objectives in designing 
this equipment were freedom from main- 
tenance and elimination of excessive 
noise. Freedom from maintenance is 
accomplished by elimination of heating 
of the mechanism and by use of the ec- 
centric movement which has relatively 
little wear. The noise is reduced by the 
eccentric movement, since the accelera- 
tions are low due to the use of eccen- 
trics instead of cams. 

It has been found from experience 
that it is necessary, in order to have 
steady background projection, to have 
pilot-pins that give positive registration 
using the same holes for projection as 
used in exposing the original film. Thus 
the present projectors in most Holly- 
wood movie studios are built around a 
camera movement having pilot-pins. 

The film in this movement is guided 
through a narrow channel composed of 
very light steel-plates which reciprocate 
in a direction parallel to the lens axis 
in order to push the film on and off 
the pilot-pins. In order to reduce the 
inertia it is necessary to make the plates 
as light as possible; consequently the 
spill light that strikes the plates causes 
them to warp and, in time, to require 
considerable maintenance. 

The new projector using the eccentric 
movement similar to the Mitchell cam- 
era movement has a fixed film-race, with 
the pull-down claws and pilot-pins enter- 
ing the film in this fixed race and mov- 
ing it in the direction of travel only, 
so that a heavier and more rigid con- 
struction may be used around the aper- 
ture. The movement has also been mod- 
ified to accommodate a very large angle 
of light. 

The regular pilot-pin bearings have 
been offset downward so that they do 
not interrupt any beam of light, and at 
the same time, the bearings themselves 
are removed from the heat so that the 
pins will not freeze due to oil evaporat- 
ing from the bearings if subjected to ex- 
cessive heat. 

• Filling the Aperture 

The present method of illuminating 
the aperture in order to get a reasonably 
uniform light on the film is to cover 
an area of several inches in diameter 
on the front of the projector and to use 
only the center portion of this area. 
This method necessarily throws consid- 
erable heat on the projector with a cor- 
responding rise in temperature, sufficient 
at times to cause the mechanism to 

To overcome this difficulty a radiator 
consisting of a series of fins extending 
from the edge of the usable light-beam, 

tj. Soc. Mot. Pict. Eng., XXXII (April, 1939). 

outward in all directions for approxi- 
mately lYz inches, was placed between 
the lamp and the main body of the pro- 
jector. This radiator defines the light 
that falls upon the aperture and pre- 
vents any spill light from falling upon 
the main body of the projector. The 
radiator is insulated from the main body 
of the projector by means of a thin disc 
of relatively poor conducting material 
so that a rather steep gradient is main- 
tained between the radiator and pro- 

The difference of temperature is of 
the order of 100 °F across approximately 
Vi inch of non-conducting material. Thus 

the difficulties caused by excessive heat- 
ing of the mechanism are removed. 

The projector is equipped with an 
interlock motor and synchronizing de- 
vice for setting the shutter in phase with 
the camera shutter after interlock has 
been established. 

Probably the most interesting ques- 
tion in connection with a projector of 
this type is: "Is the picture steady?" 
In answering this it can be pointed out 
that the projector has been tested in 
several of the major studios both visually 
and photographically, and has proved 
itself capable of projecting extremely 
steady pictures. The machine is at 
present being used by Technicolor in 
some experimental work to demonstrate 
the possibility of process work in con- 
nection with their system of color pho- 
tography, and has proved quite satisfac- 
tory for such use. 

Major N. Y. Strike Looms as I. A. Demands Exchanges 
Deny Film to Non-I. A. Theatres; Legal Angles 


STRIKE of major proportions 
carrying with it the threat to tie up 
the entire theatre field in N. Y. City 
loomed as this issue of I. P. went to 
press as a result of an unprecedented 
strike order issued by I. A. Local 306 
against projection rooms in the home 
offices and the exchanges of all major 
film companies. L. 306 seeks to com- 
pel the distributors not to deliver film 
to the approximately 75 non-306 theatres 
in N. Y. City against which the union 
has waged an unsuccessful organizing 
drive for many years. 

Immediately following issuance of the 
L. 306 strike order, its sister I. A. Local 
52-B, which includes all exchange 
workers, announced that its members 
would not cross the L. 306 picket lines. 
This move threatens to paralyze film dis- 
tribution to all N. Y. theatres. It is 
considered highly probable that other 

Pre-Show Print Inspection Urged 
By Canadian Exhib. Unit 

Attention of the members of the Inde- 
pendent Theatres Assoc, of Toronto, 
Canada, has been called by its leaders to 
the fact that under the standard license 
agreement the exhibitor is held responsible 
for damage to film by fire, but there is 
one way in which the responsibility for 
such fires can be shifted to the distributor. 

The Assoc, contends most theatre fires 
are caused by film tearing and clogging the 
machine long enough for the heat of the 
carbon to ignite the film, and therefore 
"most fires of this origin are caused by the 
faulty condition in which films are delivered 
to subsequent-run theatres," and that "re- 
vivals are in notably bad condition." 

Exhibitors are advised to "have your pro- 
jectionist examine all film prior to show- 
ing, make out a report on the condition of 
any damaged film" and to "mail this re- 
port to the exchange before show time." 
It is stressed that "this report constitutes 
evidence"; and "should a fire result from 
the condition of the film, the liability can 
be traced to and fixed on the distributor." 

I. A. locals in the N. Y. area — includ- 
ing 54, studio mechanics; 702, lab. 
workers; and 644, cameramen — would 
progressively lend support to the strike. 
This move of Local 306, generally re- 
garded as having been planned in its 
entirety by the I. A. General Office, is 
the first attempt by the International to 
utilize its industry-wide organized units 
to force the unionization of non-I. A. 
theatres. It is understood that N. Y. 
City was selected as the proving ground 
for this experiment because if its ex- 
treme vulnerability as the first line in 
the industry's distribution system, in 
addition to providing an admirable test 
case because of the existence of theatre 
contracts with a union other than I. A. 

• The Distributor Stand 

This strike is regarded in legal circles 
as of questionable legality for a number 
of reasons. First, there is the dis- 
tributor contention that compliance with 
the demands of L. 306 would place the 
film companies in violation of contracts 
to deliver film already bought by the 
independent theatres, against which the 
strike is directed. 

It was on this ground that the trustee 
for R.K.O. (in receivership and therefore 
subject to Federal Court jurisdiction) peti- 
tioned Federal Judge Bondy for instructions 
as to what action to take in the situation. 
The petition said failure to deliver films 
might bring suits for breach of contract; 
and it asked the court to advise whether 
the demand of L. 306 was legal. The court 
was also requested, in the event it held the 
union's demand illegal, to lauthorize the 
trustee to bring suit for an injunction 
against the union on the ground of coer- 

Judge Bondy advised the company to en- 
deavor to carry out its contracts while seek- 
ing to negotiate a settlement with the 
union. At the same time, however, the 
court indicated that the company was free 
to seek an injunction against any act it 
deemed unlawful. 

Counsel for the R.K.O. trustee told the 



court that yielding to the union's demand 
might place the company in the position 
of having violated the anti-trust laws in 
cooperation with the union. Counsel for 
L. 306 denied there was any such danger. 
Lawyers freely predict the issuance of in- 
junctions against the union. In some quar- 
ters, however, it is held that distributors 
are protected against exhibitor suits for non- 
performance by the "causes beyond our 
control" clauses in film contracts. 

Other Legal Considerations 

Another interesting angle of the situation 
is the existence of contracts between the 
independent theatres involved and a non- 
I. A. affiliate (Empire State Union). Law- 
yers hold that the Empire group has been 
duly chartered by N. Y. State, that its 
contracts are wholly valid, that its members 
have a right to work no less than do mem- 
bers of L. 306, and that under existing 
labor laws Empire certainly is the author- 
ized bargaining agent for these men. 

Thus, even should the distributors accede 
to the demands of L. 306, which action is 
extremely doubtful, the theatre owners 
could hardly escape a suit by Empire State 
Union on non-performance of contract. 
Then, too, there is the possibility of a suit 
by the exhibitors against the I. A. for dam- 
ages stemming from the action by the latter. 

It is admitted by all parties concerned 
that I. A. exchange workers and projection- 
ists cannot be forced to work, but this 
merely gives rise to another question as to 
what course would be pursued by the dis- 
tributors when confronted by an indefinite 
closing of their exchanges. Of course, I. A. 
could refuse to let its theatre projection- 
ists handle film produced by non-I. A. ex- 
change workers. 

Move Constitutes Precedent 

This strike action by the I. A. certainly 
constitutes some sort of precedent in the 
annals of American industrial relations. It 
is a not uncommon move for a labor union 
to refuse to handle the product of non-union 
labor, whether in transport or for some 
additional work necessary to turn out a 
finished article. Such non-union products 
are commonly known in labor circles as 
"hot stuff." The Teamsters International 
has extensively used this means to bar the 
transportation of products originating in 
non-union sources. The idea has also been 
applied extensively in quarrels between 
A. F. of L. and C.I.O. units, and there 
are even cases on record where A. F. of L. 
units have used the device in jurisdictional 
squabbles among themselves 

The current N. Y. City stand of I. A., 
however, is unique in that the product at 
issue, motion picture film, is not only han- 
dled from raw stock to completed print by 
(Continued on next page) 


A microphone, known as Model 77-C, 
which combines in its compact, streamlined 
case all the characteristics of three differ- 
ent type microphones, making it ideal for 
radio, movie or any public address use, is 
announced by RCA. A handy switch at 
the base makes the new unit uni-directional 
bi-directional or non-directional instantly, 
and permits almost, limitless applications. 

With the control switch in the uni-direc- 
tional position, the instrument picks up only 
sounds reaching the front, or live side — 
turning a deaf ear to those emanating from 
any other angle. As a bi-directional micro- 
phone, it performs like an ordinary velocity 
instrument, being responsive on only two 
sides. In the third position, the control 
switch permits sounds coming from any 
angle to be picked up. 









Main Drive Gear Breaks 
on Sunday: Projectionist 
Calls Altec Inspector 

Time: 4 p.m. on a Sunday afternoon. 

Place: A theatre in Wisconsin. 

Five minutes before 4 P.M. the main drive gear in one of the pro- 
jectors broke, and the stripped teeth fell into the gears of the sound 

"The Altec man can fix the sound reproducer, but where in hell are 
we going to get a new gear for the picture head— on Sunday?" ex- 
claimed the projectionist. 

Grabbing the phone, he called the Altec inspector in Milwaukee. 
The projectionist told him what had happened and stated that the 
sound reproducer drive shaft appeared to be sprung. The Altec inspec- 
tor explained to him how to check the location of the projector head 
to determine whether it had shifted when the main drive gear broke, 
pointing out that the shifting would cause the sound drive shaft to 
bind and appear to be sprung. With this information, the projectionist 
checked his equipment and found that the sound drive was okay. 

In the meantime, the Altec man got busy. He located an employee 
of a local supply house at his home, got him to ship out the replace- 
ment gear right away. 

Getting a new gear wasn't a sound problem. True, but the projec- 
tionist knew that no matter what kind of help he needed, he could 
freely call on the Altec man. 



250 West 57th Street • New York City 


MABCH 1939 






You owe il 

to yourself! 

BECAUSE • • • They are mod- 
ern, dependable and economical. 

BECAUSE ... They are the 
only rectifiers using tested P. R. 
Mallory Magnesium - Copper Sulphide 
rectifying units, whose immunity to 
projection room heat factors has been 

BECAUSE ... They meet suc- 
cessfully and efficiently the amperage 
requirements of today — even when two 
lamps or a spotlight must be operated 
from ONE Rectifier. 

BECAUSE ... The simplicity 
of construction found only in Mag- 
nesium-Copper Sulphide Units is your 
VISIBLE guarantee against needless 
multiplicity and complications. 

BECAUSE ... The reliable 3- 

phase fan — magnetic switches — protec- 
tive fuses — sturdy and scientifically de- 
signed outer ONE PIECE case— all 
are exclusive Forest features. 

BECAUSE ... They solve, with 
ease, all the problems encountered in 
present-day projection power supply. 

BECAUSE ... They are DE- 

Write for Information 




(Continued from preceding page) 

members of the A. F. of L. but even by the 
members of only one affiliate thereof, and 
that the I. A. itself. This poses the very 
interesting question as to the ability of a 
union to determine not only the labor con- 
ditions under which a product may be 
manufactured but also to retain the de- 
cisive voice as to its ultimate disposition 
and consumption. Lawyers hold that under 
these circumstances the N. Y. City situa- 
tion inevitably must tangle with the com- 
merce laws of the U. S. 

These, and possibly other, questions all 
must be answered before the N. Y. City 
situation is settled — provided no party to 
the matter gives way pending final adjudi- 
cation. At the moment, however, the issue 
is joined, and it is one fraught with im- 
mense significance to the I. A., to the dis- 
tributors, to exhibitors, and to non-I. A. 
unions. — J. J. F 

Oil-Parafine Treatment For 
Mirrors Frowned Upon 

From J. A. Campbell of Miami, 
Florida, comes the following note anent 
the refurbishing of mirror reflectors: 

"Have recently run across a brother 
projectionist who works on Suprex 
lamps, the reflectors for which are in 
need of replacement or resilvering. He 
tried cleaning them in several different 
ways; finally one day he deliberately 
rubbed them with an oily rag. 

"Liking the result of the oil treat- 
ment, he cleaned them again, and after 
getting them hot in the machine, took a 
block of parafine and rubbed it over 
the surface. The parafine spreads 
freely on the hot glass, after which the 
projectionist gives it a high polish with 
a clean rag, removing the surplus oil. 

"The results of ,this treatment are 
apparently good. Could I. P. give us a 
report on this procedure — that is, let us 
know just what happens under these 
circumstances. Or, are we just kidding 

• Foresee Oil Trouble 

To which is made the appended reply- 
by Dr. W. B. Rayton of Bausch & Lomb 
Optical Co: 

"The process described does not im- 
press us as one likely to make any 

permanent improvement in the perform- 
ance of the reflector. Certainly, if the 
reflector is in need of resilvering, no 
treatment given the front surface of it 
can take the place of the required re- 
silvering, for I assume he is using a 
standard mirror with the silver on the 

"The application of any organic oil 
to the front surface of a mirror exposed 
to the heat of a motion picture lamp- 
house would seem to me to promise con- 
siderable trouble as a result of the 


A new process of third dimensional pic- 
tures, said to differ entirely from all previ- 
ous attempts to obtain films in relief, has 
been invented by M. Barraud, of Paris, 
France. The system is called Neo-Relief. 
M. Barraud claims that Neo-Relief neces- 
sitates no modification in either projector 
or screen, nor does it require the wearing 
of special spectacles by the spectators. It 
does require a change in camera, however. 
An early demonstration is promised. 

Gradationally Perforated 

Tests show that a serious loss of 
light begins one- third of the dis- 
tance from the center of the pic- 
ture area and increases sharply 
to a light loss greater than 33 1/3% 
at the sides. This loss is elimin- 
ated in the Even-Lite Screen. 


Exclusive Sales Agents 


145 Valley St., Belleville, N. J. 

All New 

Anrwurwing . . . Ck ^X 

For all projectors and sound equipments 

AH take-ups wind film on 2, 4 or 5 inch hub reels. 

The Clayton Rewinder 

For perfect rewinding on 2000-foot reels. 


31-45 Tibbett Avenue New York # N. Y. 



evaporation of most of the oil, leaving 
some sort of a gummy residue on the 
surface that would again reduce the 
efficiency of the mirror. 

"One condition that seems likely to 
be improved by such a treatment would 
be one in which the front surface of 
the mirror is badly scratched or pitted, 
causing a considerable loss of light due 
to diffuse reflection. An oil that filled 
the scratches and pits would bring 
about an improvement, but I would not 
expect it to last for any length of time." 

Maine 'Safety' Shutter Bill Draws 
Exhibitor, I. A. Fire 

A Maine legislative bill to require instal- 
lation of a "safety" shutter between the in- 
flammable film and the light on theatre 
motion picture projectors to prevent fires 
was termed by opponents at a hearing "an 
attempt to legislate a costly, untried and 
unnecessary device into Maine theatres." 
Theatre owners, told legislators that the 
device had not been offered to theatre 
owners in this region. 

Proponents of the bill, said the device 
would stop instantly hot light rays in a 
projector when breaks or other stoppages 
occurred, doing away with fire hazards. 
R. W. Gustin and B. J. Dorsky, both of 
llie Bangor I. A. Union, opposed the instal- 
lation of the device because it would not 
"banish the flame-flash on the screen caus- 
ing panic, nor materially aid in cutting 
down hazards of operation." 


Century Electric Co., of St. Louis, Mo., 
has completed arrangements with Erpi 
whereby the latter firm will act as exclu- 
sive distributor for Century generators in 
Mexico, Central America, West Indies and 
certain So. American countries. 


Operating theatres in the U. S. on Jan. 
1 last totaled 15,701, representing a drop 
of 550 active theatres in the preceding 12 
months, according to a nation-wide survey 
completed recently by Film Daily. Total 
number of seats is 9,996,830, as compared 
with 9,855,325 in the 16,251 active houses 
on Jan. 1, 1938. Figures indicate a high 
mortality among the smaller theatres. 

U. S. theatres closed as of Jan. 1 num- 
bered 2,128, with an aggregate seating 
capacity of 826,910. Comparable figures for 
Jan. 1, 1938 were 1,931 and 801,981. 


International Projector Corp. announces 
that Erpi has been appointed exclusive dis- 
tributors of Simplex projectors in Brazil, 
China, Malay States, Straits Settlements, 
Siam, French Indo China, Borneo, Sarawak, 
Netherlands East Indies, Australia, and 
New Zealand. Simplex projectors have 
been sold for many years by responsible 
distributors in many foreign countries, and 
the arrangements with Erpi complete this 
world-wide distribution setup. 


The Detroit office of Altec Service Corp. 
has moved to larger quarters in the same 
building, at 2111 Woodward Avenue. 


Twenty-two units of the I. A. in 18 Iowa 
towns are straining to defeat a bill intro- 

Read These Reasons — 


Tops the Field Because — 


It Offers 

Better screen illumination regardless of make, size and type — Minimum cost 
in current and carbons: MORE LIGHT PER AMPERE!— Maintenance is 
negligible — Every lamp guaranteed mechanically for one year — Has every 
known proved improvement — Modern and simple to operate — Costs no more 
than lamps of inferior quality — Guaranteed by the oldest and largest manu- 
facturer of projection lamps — Practical for either the 500-seat or 5,000-seat 

At Independent Theatre Supply Dealers Everywhere 
In Canada: Dominion Sound Equipments, Ltd., Montreal, Quebec 


47-31 Thirty-Fifth St. 

Long Island City, N. Y. 

duced in the State Legislature to ban bank 
nights. More than 300 I. A. members, it 
was announced, are working with theatre 
managers to retain bank nights, which are 
held in an estimated 200 Iowa theatres 


Altec Service Corp. will service Minne- 
sota Amusement theatres in Minn., No. and 
So. Dakota and Wise. With this deal, in 
addition to those already made with Rand- 
force; Wilmer & Vincent, and Griffith 
Amusement circuits, a total of over 250 

theatres have signed with Altec during the 
past month. 


A catalog of the new Supreme line of 
testing instruments is now available for all 
readers of I. P. upon request to Supreme 
Instruments Corp., Greenwood, Miss. Men- 
tion I. P. when writing to company. 


Sales of 16 mm. sound projectors for all 
sources, including portable road show units, 
increased by more than 33% during the 

MARCH 1939 


Some of the Reasons Why Projectionists Prefer 


.Quiet operation . . . utmost dependability . . . continuous 
delivery of non-pulsating current at the exact voltage 

There are many other reasons for specifying the 

Sold through The National Theatre 
Supply Co.; In Canada, General 
Theatre Supply Co.; or write us 



12692 Elm wood Avenue 


Cleveland, Ohio, U. S. A. 

Exclusive Manufacturers of the Transverter 

last part of 1937 and in 1938. Prospects 
are for equally good business during 1939. 


The perennial favorite of Nebraska pro- 
jectionists, the bill providing for a toilet 
in projection rooms in all cities of more 
than 10,000 population, has been killed in 
committee. A bill prohibiting walkathon 
contests, backed by the film business, was 


Eastman Kodak net profits for the year 
ending Dec. 31 last were $17,339,408, as 
compared with $22,347,345 for the previous 
year. Dividend on common stock is $7.54 
per share, as against $9.76 a year ago. The 
company paid a two-million dollar wage 
dividend to employees on March 27. 


Representative of Baird Television Co. of 
London, Eng., is now in the U. S. to explore 
the possibilities of manufacturing television 
receivers for theatres, preliminary tests of 
which have proven highly successful in Eng- 
land. Estimated price per theatre is from 
$5000 to $7000 for unit giving a 15 x 12 ft. 
screen image. Baird seeks a Broadway, 
N. Y. theatre for demonstrations. 


(Continued from page 17) 

of the two push-pull 205-D rectifier 
tubes which obtain their plate voltage 
from the winding 5-6-7 of the power 

(as was the trouble in this case), one 
of the rectifier tubes was rendered in- 
operative, and the current in the plate 

circuit dropped approximately 50 per 

However, when the projectionist 
short-circuited R-6 and R-7, he reduced 
the grid bias on the remaining tube to 
zero, which caused the plate current of 
this tube to increase to where it ap- 
proximated the normal plate current of 
both tubes operating normally. When 
the plate current approached normal, 
the control circuit caused the motor to 
develop sufficient power to bring it up 
to normal speed. From there on, the 
motor was able to carry on its own. 

• Paging A Tin Bucket 

The following story is still another 
one about a motor, but in this case, in- 

stead of the motor acting like a kid that 
didn't want to get to school on time, 
it acted like a whippet chasing the rab- 
bit, in other words, when the Altec 
inspector received a call from the Ar- 
cade Theatre in Brookhaven, Mass., it 
was a case of one machine racing over 
speed, and the speed couldn't be regu- 

Knowing the idiosyncracies of that 
motor very thoroughly, the Altec in- 
spector knew just what to tell the pro- 
jectionist he could do until the inspector 
could get to the theatre. What he told 
him on the 'phone was, if you'll excuse 
my talking in riddles, how to operate 
a motor control cabinet type motor — 
without a motor control cabinet! 

He told the projectionist to obtain an 
ordinary bucket, having an unpainted 
interior. Then to fill it with salt water 
made up of two or three ounces of table 
salt for each gallon of water. Next, the 
projectionist was to disconnect the leads 
from the motor which normally go to 
Terminals 3 and 4 of the 708 A control 
cabinet, connect one of these leads to 
the metal bucket, and connect the other 
lead to a piece of arc carbon. Then, he 
told the projectionist to immerse the 
piece of arc carbon in the salt water in 
the bucket, and to raise and lower — ad- 
just the depth, that is — the carbon into 
the salt water until the motor operated 
to give approximately 90 feet per min- 
ute film speed! 

By this makeshift arrangement, a very 
effective water rheostat was improvised, 


Altec Service Corp. has made arrange- 
ments with National Theatre Supply Co. to 
act as the latter's agent in stocking and 
distributing replacement parts for all types 
of 4-Star Simplex sound systems. Parts 
will thus be available from Altec stock 
points and warehouses during all theatre 
operating hours. 

transformer in the control box. 
one half (6-7) of this winding 

<gltflMte SAYS- 


"Every time that phone rang, I 
knew the boss was complaining 

about the sound, 
nothing I could do 
the new Simplex 





But there was 
Then we got 

Sound System. 
He hasn't 




which could be accurately adjusted to 
cause the motor to operate at its normal 
r.p.m. As the Altec inspector explains 
it, here's the why-and-wherefore: 

The drive motor involved was essen- 
tially of the repulsion type — that is, its 
speed is controlled by the external re- 
sistance in the armature circuit. Nor- 
mally, the delicately adjusted circuits of 
the motor control cabinet automatically 
control this external resistance, so that 
the motor maintains a normal speed. 
However, the control cabinet can be dis- 
pensed with, and the motor made to 
operate at approximately normal speed 
by placing an adjustable resistance or 
rheostat in the external armature cir- 
cuit and adjusting it manually. That's 
just what was accomplished by means 
of the homeopathic water rheostat at the 
Arcade Theatre. 

• A Word To The Wise 

Well, those are the stories I dug up 
this trip. But let me add to them just 
one word — accompanied by a very em- 
phatic wagging of my finger — on the 
subject of playing tricks like this un- 
less you know exactly what you're 
about, or unless the Altec service in- 
spector says it's okay. I need only re- 
mind you that the power transformer 
in this motor control cabinet delivers 
a fairly husky current at 450 volts — or, 
in plain English, it can give you a 
shock the size of a healthy kick from a 
Jersey mule that's feeling awful mean. 
High voltage hazards are high voltage 
hazards, aren't they? 

The stories themselves? They're 
pretty slick about some pretty slick 
cooperating, aren't they? 


(Continued from page 11) 

taken from the film being projected, 
which automatically throws a switch 
to set in operation the incoming pro- 
jector. At another point a cue is taken 
which actuates the douser control switch 
while at the same time operating the 
sound changeover. All parts are con- 
tained in a control cabinet mounted on 
the wall. Included are mechanical and 
electrical interlocks controlling the 
starting and stopping of motors, dousers 
and the sound. 

• Manual Aid Required 

This method requires manual reset- 
ting for each reel, thus efficient opera- 
tion is somewhat dependent on the 
human factor. However, it does remove 
the need for the projectionist standing 
at a porthole to observe cues, thus re- 
leasing him for other duties. 

D. Friction disc method. As the 
nlm unwinds from the upper magazine, 

Dfe Luxe projection is yours with this steady, 

brilliant, snow-white light. .. . It's essential to 

proper projection of color pictures. 

For sale by Independent Theatre Supply 

Dealers everywhere. . . Demonstration 

without obligation. 

Write today for free catalog on Strong 

unconditionally guaranteed products . . . 

your guide to better projection. 




Export Offirr: Room 2002, 22fr Wr 42ml Btrwt-N«w-*«i. Gi«v 

How Many? 

Was this copy dog-eared when it came to you? How 
many men read it ahead of you? 

You would receive a clean, fresh copy if you had a 
personal subscription — and you wouldn't have to 
wait — you would be first to read it. 

Use coupon below. 

580 Fifth Ave., New York, N. Y. 

□ 1 year — 12 issues — $2.00 

□ 2 years — 24 issues — $3.00 
Foreign: Add 50c per year. 

Enter my subscription for 



City State 

MARCH 1939 


the speed of the reel therein increases. 
A friction disc attached to the upper 
magazine shaft drives a rotatable shaft 
on which is a pair of fixed sleeves. 
Weights are connected to these sleeves 
by means of pivoted links, causing an 
outward movement of the weights when 
the shaft rotates. 

Increasing reel speed, as previously 
mentioned, causes the weights to pull 
outward, thus pulling the sleeve upward 
to a contact which closes the circuit and 
sets off an alarm. Variation in the time 
setting is accomplished by adjusting a 
set screw. Although a setting for a 
time interval can be made on each pro- 
jector, it is necessary to operate a 
double-pole switch manually after each 
reel in order to receive a signal on the 
following reel and at the same time 
shut off the warning on the current reel. 

E. Roller arm mounted in upper 
magazine. A set screw in this arm per- 
mits adjustment for an approximate pre- 
determined interval, depending upon the 
amount of film still on the reel. When 
this point is reached by a small wheel 
riding on the emulsion, a spring action 
rings a bell. Varying thicknesses of 
film, splices, and reel diameters will 
naturally cause a variation of the tim- 
ing. Approved exchange practice does 
not favor anything that functions 
through contact with the film. 

F. Audio-visual dial signal. This is 
essentially a clock mechanism which is 
wound by a single twist of a combination 
pointer and knob. At the start of a 
reel the knob is turned until the pointer 
touches zero; pointer's position at end of 
reel indicates both the running time and 
the footage. 


These films have been prepared under the supervision of the Projection 
Practice Committee of the Society of Motion Picture Engineers, and are 
designed to be used in theaters, review rooms, exchanges, laboratories, 
factories, and the like for testing the performance of projectors. 

Only complete reels, as described below, are available (no short sections 
or single frequencies). The prices given include shipping charges to all 
points within the United States; shipping charges to other countries are 

35-Mm. Visual Film 

Approximately 500 feet long, consisting of special targets with the aid 
of which travel-ghost, marginal and radial lens aberrations, definition, 
picture jump, and film weave may be detected and corrected. 

Price $37.50 each. 

16-Mm. Sound-Film 

Approximately 400 feet long, consisting of recordings of several speak- 
ing voices, piano, and orchestra; buzz-track; fixed frequencies for focus- 
ing sound optical system; fixed frequencies at constant level, for de- 
termining reproducer characteristics, frequency range, flutter, sound- 
track adjustment, 60- or 96-cycle modulation, etc. 

The recorded frequency range of the voice and music extends to 6000 
cps.; the constant-amplitude frequencies are in 11 steps from 50 cps. to 
6000 cps. 

Price $25.00 each. 

16-Mm. Visual Film 

An optical reduction of the 35-mm. visual test-film, identical as to 
contents and approximately 400 feet long. 
Price $25.00 each. 

Address I 


Hotel Pennsylvania New York, N. Y. 

Each reel is given a consecutive num- 
ber. A numbered marker is placed over 
the dial to indicate exact running time 
of each reel, remaining in place during 
entire run of show. Projectionist sets 
pointer to ring bell at any predeter- 
mined interval, either for striking the 
arc or to signal approach of cue mark. 
This operation is performed for each 
reel on which an audible signal is de- 

After the pointer is set, projectionist 
is able to observe remaining running 
time from a considerable distance. When 
actual reel footage is known, the time 
equivalent is noted on the dial. This 
device is not connected to the projector 
in any manner but is mounted on either 
the wall or the rewind table. It requires 
a manual motion to set for reel end sig- 
nal. If no setting is made, this is evi- 
dent by position of pointer at zero. 

An upper magazine has recently ap- 
peared on the market which is equipped 
with a built-in signal device. This con- 
sists of a shaft attached to which is an 
arm having at its end a wheel which 
rides on the film. When the end of the 
reel approaches, a spring is released 
which sets off a bell signal. Notches 
are placed on the outside of the maga- 
zine, and by means of a pointer operat- 
ing in conjunction with the inside arm, 
the projectionist has some measure of 
visual indication as to the amount of 
film run off in the upper magazine. 

All these methods have as their com- 
mon purpose an effort to run a smoother 
show. More cooperation between pro- 
ducers, exchanges and exhibitors would 
go far toward eliminating current evils 
in projection without the aid of any of 
the devices hereinbefore mentioned. Pro- 
ducers and their exchanges still handle 
prints on the basis of total running time 
of the subject — and herein may lie the 
reason for much of our troubles in this 

Each reel should be marked for exact 
footage, which would enable the pro- 
jectionist to set up a schedule indicative 
of the exact time for the showing of 
each subject, much after the fashion of 
program timetables now made up for 
patrons' convenience. But where, oh 
where, is that cooperation between ex- 
changes and projectionists without 
which keeping track of reel footages is 
an impossible task? 

Personally, the writer can see no need 
for further overloading projector basis 
or cluttering up the walls or any other 
space in the projection room with ad- 
ditional equipment which inevitably 
serves only to increase the projectionist's 
duties and responsibilities by requiring 
attention to additional apparatus — thus 
defeating the very purpose for which 
it was intended. 



The Strong ZIPPER Changeover 

Made by a Projectionist for Projectionists! 

Offering Exclusive Patented Features Adaptable to All Makes of Projectors 









FOR ^ 







ZIPPER Changeovers for all mod- 
els mount directly on the projector 
at the aperture and can be in- 
stalled within 10 minutes without 
any drilling or tapping, etc., and 
require no brackets! A new-type 
treadle foot-switch, utilizing an 
unbreakable mercury switch, elim- 
inates all switch trouble. Weighs 
only 20 ounces; guaranteed against 
trouble for one year after purchase. 

The combination Sound-Vision 

Changeover is now available in 
all ZIPPER models for use with 
any RCA sound installation. This 
method of changeover is EXCLUS- 
being fully covered under U. S. 
Patent No. 1,796,970. These com- 
bination models for RCA systems 
are priced at $125 per pair, includ- 
ing foot-switches. 

• • • 

Strong ZIPPER Changeovers are 
especially designed and fitted for 
the following mechanisms: 

The New E-7 
The Super-Simplex 
Standard Rear Shutter 
Standard Front Shutter 
With B. & S. Rear Shutter 
With Wenzel Rear Shutter 

• • • 

All Models 

• • • 



Exclusive Patented Feature 

Zipper Changeovers are available equipped with a sound 
switch so that sound and picture can be changed over simul- 
taneously by merely stepping on the foot-switch. When so 
equipped, an auxiliary switch is provided for disconnecting 
the automatic changeover, so that the sound can be run off 
on one projector while the picture continues on the other. 

Only Strong Offers This Feature 

PRICE ON ALL MODELS: $60 per pair 

With Treadle Mercury Switches: $75 




L. D. STRONG, President 
Makers of Electric Changeovers for 20 Years 

908 So. Wabash Ave. Chicago, EL. U. S. A. 





















25c A COPY • $2 A YEAR 

High Fidelity 


Long Life 




Get spare photocells for your 
projectors. It pays. Order 
from your supply dealer! 


Dept. J - 1731 Belmont * Chicago 


Visitron cells are available for every type of sound projec- 
tion equipment. Theatre supply dealers can advise the 
correct cell for your equipment. Buy from your supply 
dealer. For information on checking the efficiency of old 
photoelectric cells, write direct to G-M Laboratories, Inc. 

Heres an important fact to remembei — Hollywood is 
now producing finer sound than ever before — because 
movie fans demand good sound. To properly reproduce 
it — and build up your business — install 

RCA Photophone Magic Voice of the Screen 

Let's look at facts. You can 
J show the finest pictures in the 
world — but you'll have empty 
seats in your theatre if the sound 
is poor. Because nowadays movie 
fans know good sound from bad 
— and patronize the theatre where 
lis tening is as much fun as looking. 
Hollywood knows this and 
that's why Hollywood puts such 
excellent sound on its films. But 
how about you — are you letting 
an outmoded sound system hurt 
your takes? 

It will pay vou to find out about 
the new RCA Photophone Magic 
Voice of the Screen. For here's the 
equipment built for true reproduc- 
tion of modern movie sound. It's 
the tonic your box office needs. 
And its low cost will surprise you, 
just as its many new features will 
delight you. Full details from your 
RCA Photophone representative. 

Better sound means better box office — and RCA 
tubes mean better sound. 

RCA Pbotophone's service organization has a 
low cost theatre service plan in which you'll he 

-available at Low Cost to 
Theatres of Every Size I 

Obsolete equipment costs you money 
in more ways than one! 




RCA Manufacturing Co., Inc., Camden, N. J. — A Service of the Radio Corporation of America 

Only the New Magic Voice 

of the Screen offers all 

these Features! 

This splendid new equipment gives 
you full assurance of constant film 
speed by adding the amazing new 
Shock Proof Drive to the famous 
Rotary Stabilizer! Besides this 
great feature, the new Magic Voice 
brings you new styling, new protec- 
tion, new convenience,' new added 
reserve power and many other out- 
standing proofs that it's the best 
value you've ever seen! Ask your 
RCA Photophone representative 
for complete information. 

APRIL 1939 


% You have many patrons who are loyal to your 
theater, who return again and again rather than go 
elsewhere. This steadfast patronage may be due to 
convenient location, to the programs you select, or 
even to personal friendship hut, whatever the motive, 
these patrons deserve recognition. 


If you are still using old style, low intensity projec- 
tion, these steady customers have a right to object. 
And some day they will. Simplified High Intensity 
projection gives so much more — easier vision; more 
accurate color reproduction; a more satisfactory level 
of general illumination. Theater patrons know this, 
for thousands of theaters have already installed it. 
The cost is surprisingly Ion: 

Ask your dealer's salesman for the booklet, "YES, BUT WHAT WILL IT COST?" 




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Unit of Union Carbide HIM and Carbon Corporation 

General Offices: 30 East 42nd Street, New York, N. Y. 



MAY **4 IHJ3 ©C1B 417035 


Edited by James J. Finn 

Volume 14 

APRIL 1939 

Number 4 

Index and Monthly Chat .... 5 

Supplementary Sources of Serv- 
ice Data Anent Sound Sys- 
tems 7 

Aaron Nadell 

The Epoch of Progress in Film 

Fire Prevention 10 

Alfred L. Sulzer 

Giant Twin Projectors Feature 
Novel Eastman Fair Exhibit. 12 

Seventh Subscription Contest 
Diagram 14 

An Analysis of Light : Termin- 
ology and Procedure in Plot- 
ting Curves 15 

National Carbon Company 

I. A. Coast Autonomy Battle; 
N. Y. City Strike Illegal— 
D. of J.; St. Louis Receiver. 17 

Proper Viewing of Motion Pic- 
tures 18 

Ben Schlanger 

The Editorial Page 19 

News Notes 
Technical Hints 
Miscellaneous Items 

Published Monthly by 



Circulation Manager, Ruth Entracht 

Subscription Representatives 

Australia: McGills, 183 Elizabeth St., Melbourne 
New Zealand: Te Aro Book Depot, Ltd., 64 Courtenay Place Wellington 
England and Dominions: Wm. Dawson & Sons, Ltd., Pilgrim St., London, E. C. 4. 

Yearly Subscription: United 
States and possessions, $2 (two 
years, $3) ; Canada and foreign 
countries, $2.50. Single copies, 
25 cents. Changes of address 
should be submitted two weeks 
in advance of publication date to 
insure receipt of current issue. 
Entered as second-class matter 

February 8, 1932, at the Post 
Office at New York, N. Y. under 
the act of March 3, 1879. 
Contents copyrighted 1939 by 
James J. Finn Publishing Corp. 
International Projectionist 
is not responsible for personal 
opinions appearing in signed 
articles in its columns. 

Monthly Chat 

THEATRE equipment sales are oft 
about 25 per cent from the level of 
a year ago, according to reliable esti- 
mates, yet development work on new 
equipment is at the highest level reached 
within the past ten years. Two new 
projectors, at least two new lamps, a new 
rectifier — these are but a few of the 
items scheduled for early announcement. 
Inevitably, current happenings will mean 
a sharp realignment of policies in the 
supply field. 

• • • 

Readers of I. P. who contemplate visit- 
ing the New York World's Fair are cordi- 
ally invited to avail themselves of the 
facilities of the I. P. office in the matter 
of hotel accommodations, reservations for 
amusements or for any chore which will 
help to make their visits more enjoyable. 
Ample advance notice is preferable. 

Incidentally, projection will play a 
major role at the Fair, with hundreds of 
units being utilized by exhibitors to put 
over their messages. Units range in size 
from the very small spots to the massive 
one-ton projectors used by Eastman. 
Altogether an impressive demonstration 
of projection facilities, and truly an eye- 
opener in the direction of Projection 

• • • 

A new type of shutter, reminiscent in 
some respects of those used about 20 
years ago, is now finding not a little 
favor throughout the Middle West area. 
Apparently, serious differences of opinion 
exist as to the utility and efficiency of 
these shutters, a pair of which (for low- 
and for high-intensity arcs) have been 
sent to I. P. for test. Results wiU be 
announced promptly upon completion of 
the tests. 

• • e 

THAT double-truck spread relating to 
mercury vapor lamps which appeared 
in a recent issue of Life served to steam 
up some of the boys anent the possibility 
of early adaptability of these units to 
theatre projection. Relax, boys, relax; 
nothing has occurred to change the status 
of these units since a report thereon was 
lajt rendered in these pages. True, 
there have been adaptations of these 
lamps to projection work, but on no suca 
scale as would warrant the enthusiasm 
generated in certain quarters by the Life 

• • • 

Our annual warning: Now that nice 
weather is here get out into the sun and 
gulp in huge draughts of fresh air as a 
means of stiffening resistance to the great 
gobs of carbon dust and sundry bacilli 
which have assaulted your frame through 
the winter months. A lot of the boys 
active a year ago are now sojourning (to 
use a nice term) in places like Saranac 
Lake and Arizona. 

APRIL 1939 

Built for Continuing Research 




Research workers in ERPI's 

Light Valve Department. 









- ■■ . ■-■ . 

Id i 

! r ml 

m "-i •■• 

' *^"j 



' frr* 

The Projection Room in ERPI's new 
Hollywood laboratory, where sound 
problems are studied daily and solved 
under actual working conditions. 

... to assure ever-finer 
entertainment in your theatre 

Since the introduction of sound 
in motion pictures, ERPI and Bell 
Telephone Laboratories — which 
developed the first practical ap- 
paratus—have pioneered in sound 
recording and reproduction re- 

These developments have been 
made available to the industry in 
Western Electric Sound Systems 
— used by leading producers and 
thousands of theatres throughout 
the world. 

In introducing sound pictures, 

ERPI accepted a definite respon- 
sibility to the industry. Now,ERPI 
reaffirms its acceptance of that 

Conscious that the future prog- 
ress and prosperity of the industry 
depend upon continued improve- 
ment of sound pictures through 
research, ERPI— backed by Bell 
Telephone Laboratories — will 
continue to devote its efforts to 
meeting the problems of today 
and anticipating and solving those 
of tomorrow. 

Electrical Research Products trtc 


Western Electric 

■ -. . 




APRIL 1939 

Supplementary Sources of Service 
Data Anent Sound Systems 

COMPLETE wiring and schematic 
diagrams, necessary to locating 
trouble, are not always available. 
Sometimes they have been mislaid, 
sometimes they cannot be obtained. 
There are manufacturers who do not 
supply wiring diagrams because they do 
not have them. There still are manu- 
facturers, unfortunately, who will not 
supply circuits of any kind. 

It is often possible to obtain data 
from other sources that will, to some 
extent, take the place of the complete 
schematic and wiring diagram. Like 
the diagrams, this type of information 
should be obtained far in advance of the 
day of need. 

Consider tube socket connections. 
Sockets nowadays have many terminals. 
The wiring diagram, if complete, will 
show which is which, but the schematic 
will not. If the necessary information 
cannot be obtained from the manufac- 
turer, it can often be found in the pub- 
lished data of a tube manufacturer. To 


refer to these data, it is only necessary 
to know the type of tube used in the 
socket, and that, if not shown on the 
socket, will appear on the tube itself. 

Figure 1 is a section of the "tube 
chart" distributed gratis by one prom- 
inent tube company. It is not repro- 
duced here for information, but merely 
by way of example. Only eight socket 
types are shown in Fig. 1 ; the full chart 
contains 75, and is not complete. 

Each square of Fig. 1 carries an 
identifying number in its lower right 
corner. To use these illustrations, refer- 
ence is made first to the body of the 
tube chart, which lists general charac- 
teristics such as heater current, plate 
voltage, amplification factor, and so on. 
One column of listings is devoted to 
"basing data" — that is, to numbers cor- 
responding with those shown in Fig. 1. 
The basing data number for the tube 
under consideration is used to find which 

square of Fig. 1 (or of the other 67 
squares) gives the socket diagram. 

Some manufacturers supply a data 
sheet within the carton of each tube. 
These should always be saved. Because 
there is one in every carton, they be- 
come plentiful in the projection room, 
and the tendency is to throw them away. 
Then when the data they carry are 
needed, none can be found. A simple 
file may be made of such slips, after 
which duplicate copies can be discarded 
without loss. They almost always carry 
socket diagrams, in addition to other 
information of value. 

Tube manufacturers, in some cases, 
also supply data in booklet form. Such 
books may devote one page to each tube 
type, and print the appropriate socket 
diagram on that page, no reference num- 
ber needed. (The reference number 
system is, however, becoming universal 
for the newer type tubes, in view of the 
great multiplicity of modern socket 
arrangements). Tube booklets are gen- 

APRIL 1939 

erally sold for a nominal sum, being 
too expensive to give away. The com- 
mon charge is twenty-five cents. 

It is apparent that if an amplifier has, 
for example, six tubes, and supposing 
each socket to have six connections, the 
tube socket charts must give valuable 
information concerning one end of each 
of 36 different wires — a substantial per- 
centage of any amplifier circuit. 

• Other Tube Information 
Socket details do not exhaust the use- 
fulness of the tube data sheet, chart or 
booklet. The characteristics listed in- 
clude some that are seldom of practical 
value in ordinary trouble-shooting (such 
as amplification factor and mutual con- 
ductance) ; some that are occasionally 
of value, if used cautiously, and some 
that are always helpful. The latter are 
the voltage and current data given for 
filament or heater; for meter readings 
taken on the amplifier should conform 
exactly, and if they do not, one amplifier 
fault has been definitely determined. 

The tube is always, in every amplifier, 
operated at its rated heater voltage and 
current. Moreover, since heater (or 
filament) voltage is always low, and cur- 
rent comparatively high, no allowance 
need be made for meter resistance (see 
I. P. for March, 1937, page 24) . 

Other characteristics of voltage and 
current listed for a given tube do not, 
however, always apply exactly. A tube 
can be used successfully at other ter- 
minal values than those recommended 
by its manufacturer for normal opera- 
tion, and plate and grid voltages are 
often varied by amplifier designers to 
suit their own requirements. A meter 
correction may also be needed when 
reading low-current, high-resistance cir- 

It is an excellent idea to take several 
complete sets of socket readings at times 
when the equipment is operating norm- 
ally, average small differences if any, 
and to note them on the tube data slip, 
chart or book. Departure from those 
readings in time of trouble is then an 
obvious symptom which indicates 
promptly the circuits that need investiga- 

• Resistor Data 

The complete and perfect wiring dia- 
gram shows not only the location of 
every resistor in the equipment, but its 
rating in ohms. Some resistors, further, 
have their ratings stencilled on. The 
stencil method however, is being in- 
creasingly abandoned in favor of the 
color-code method, which is cheaper, 
and less subject to loss of information 
through heat, dust and aging. The 
color code is very simple, easily remem- 
bered, and highly practical. 

Resistors change their value for any 
of a number of reasons including heat- 

ing, corrosion in some cases, or break- 
age. But the information given by the 
ohm-meter may not be very useful if the 
trouble-shooter does not know what was 
the original rating of the part. 

The resistor color code has been ac- 
cepted by all American manufacturers 
who use the color method at all, and 
will always be the same regardless of 
the origin of the part. There are three 
colors: one on the body, one at the end, 
and one in a band around the body, or a 
dot located at or about the center. They 
must be read in the correct order, body 
first, and band (or dot) last. To re- 
member the order remember the three 
letters . BEB (body-end-band) or BED 
( body-end-dot 1. 

There are ten colors, corresponding 
to the following figures: 

Brown 1 Blue 6 

Red 2 Violet 7 

Orange 3 Gray 8 

Yellow 4 White 9 

Green 5 Black 

These colors may be memorized with 
their corresponding numbers, or the list 
just given copied off and filed where it 
can easily be found. Some manufac- 
turers will send resistor color code cards 
on request. 

Reading the colors of any resistor, the 
body color, taken first, indicates the first 
digit in the ohmage rating. Supposing 
the body to be red, that digit is 2. The 


Basing views showing bottoms of the 

next color, end, gives the second digit. 
If it is yellow, the corresponding digit 
is 4. The band or dot color does not 
stand for a figure, but for the number of 
zeros to follow after the first two figures. 
If it is black, no zeros follow in the ex- 
ample given, and the rating is 24 ohms. 
If, however, the dot in the same example 
is brown, 1 zero follows, and the rating 
is 240 ohms. It is obvious that inter- 
mediate ratings, such as 245 ohms, or 
24,500, cannot be shown in this code. 
The nearest available rating is used in- 

Table A may be used for many com- 
mon values, although it is usually 
handier to remember the code and use 
it without reference to any tabulation 
except perhaps that of color values, as 
Listed above. In the larger tabulation 
the lefthand column or figures (which 
will be more useful in the case of con- 
denser coding, as will be seen) can be 
ignored as far as resistance is concerned, 
or treated as representing megohms. 

The right-hand column of figures rep- 
resents ohms. Next come three lines of 
colors, body, end, band. Thus at the 
bottom of the column a brown body (1) 
followed by a black end (0), followed 
by a blue band (6 more zeros) totals 
an ohmage of 10,000,000. The chief 
thing to remember is that the last color, 
the dot or band, does not represent any 
figure, but for a given number of 

The color rating must never, in any 
circumstances, be compared too literally 
with the ohm-meter reading. Discrepan- 
cies up to as much as ten per cent 
emphatically do not always represent 
trouble. In the first place the rating 
method, as just shown, does not take 
care of intermediate values. It can 
show a value of 10,000 ohms or of 11,000 
ohms, but not one of 10,500. In the 
next place many modern resistors, used 
at non-critical points of a circuit (that 
is, points where some small departure 
from rated value will have no impor- 
tant effect on performance), are not in- 
variably accurate as to rating. 
• Condenser Data 

Resistors that come within one per 
cent of their rated value are sold at a 
premium, and variations of as much as 
five per cent are not uncommon. Some 
of the cheaper types (still satisfactory 
for certain limited uses) may not come 
closer than within ten per cent of the 
resistance at which they are rated. A 
discrepancy of more than ten per cent 
generally indicates some fault, raising 
the question of whether a change in the 
value of the resistance unit in question 
could account for the type of trouble 
experienced or can in any way indicate 
the possible source of that trouble. 

Condensers are rated by a color code 













































































































































































































































































similar to that used for resistors, but 
since their shape often differs, a row 
of three-colored dots may be substituted 
for the body-end-band system. Where 
such a row of colored dots is found, an 
arrow, printed or moulded near them, 
will indicate the order in which the 
colors are to be read. 

Their numerical significance is the 
same as in the case of resistors, but it 
is important to remember that the quan- 
tity signified is not microfarads, but 
micro-microfarads, or l/l,000,000th of 
the quantity usually desired. It is there- 
fore necessary to divide the indicated 
number by 1,000,000. (The smaller the 
measuring unit used, the larger will be 
the figure that designates the equivalent 
quantity; thus 1 mmfd. is the same as 
.000001 mfd.). 

In Table A the extreme left-hand col- 
umn may be taken as microfarads, the 
column next to it as representing micro- 
microfarads. The color code will give 
results falling within the figures of that 
column, which may then be translated 
by reference to the tabulation, or more 
simply and with less delay by deviding 
by one million. 

• Miscellaneous Sources 

It should be noted that in the case 
of condensers also the color code fails 
to give intermediate values, such as 275,- 
000, but is restricted to a choice be- 
tween 250,000 and 300,000; further, that 
condensers, like resistors, do not always 
conform strictly to their rated values. 
In most cases, fortunately, a ten per 
cent condenser variation will produce 
no trouble except for a small shift in 

frequency response, probably not dis- 
cernible to the ear. 

Just as the packing slip included with 
some tubes may contain highly useful 
information not shown on the tube itself, 
so many shipments of spare or replace- 
ment parts received by the theatre are 
often accompanied by data which the 
actual part does not carry. Resistance 
or condenser ratings may be shown on 
the carton or even on the bill, and no- 
where else. 

Transformers in particular often carry 
highly pertinent data in a form which 
is detached when the part is installed, 
and then usually is lost. A power trans- 
former with many terminals for different 
voltages, or a sound transformer with 
terminals for a large number of im- 
pedances, must be marked in some way 
to show the terminal combinations avail- 
able for different purposes. 

Sometimes these data are stencilled on 
the part, and can always be found by 
brushing off accumulated dirt. More 
often the terminals emerge through a 
printed cardboard on which the neces- 
sary information appears. After the 
part has been installed (with the help 
of reference to the cardboard) the data 
are generally considered of no further 
use and thrown away. 

However, if the transformer develops 
trouble, not all of it may go bad at the 
same time. It is very possible that only 
one winding will burn out, and that 
suitable connections to other terminals 
will give an entirely satisfactory emerg- 
ency substitute for the required volt- 
age or impedance. The same is true of 
transformers equipped with color-coded 
leads instead of terminals. A data sheet 
indicating the correct color combina- 
tions for different purposes invariably 
accompanies such units; and again is 
generally thrown away when the part 
has once been wired in. 
• Availability of Data 

All such material should be saved. 
In the case of multiple-terminal in- 
formation of the kind just referred to, 
the information should be kept even 
when complete drawings of the sound 
equipment are at hand. It is unlikely 
that those drawings will give data by 
which satisfactory emergency connec- 
tions can be made to a transformer with 
one burned-out winding. 

There is no difficulty about filing use- 
ful information where it will be in- 
stantly available. No elaborate filing 
system is needed. All that is necessary 
is a folder, a loose-leaf book or even a 
simple envelope for each component 
piece of apparatus — that is, each ampli- 
fier, sound head, power unit, etc. In 
that envelope or book should go all data 
applying to a particular unit. If the 
same information also applies to some 

APRIL 1939 

other unit, it may be copied, or a cross- 
reference noted in the other unit en- 

If the schematic and wiring diagrams 
are available or can be procured, they 
constitute the most important single 
items of information. They alone may 
be left bound in an instruction book, 
rather than filed, provided they are re- 
ceived that way. Meter readings re- 
corded when there is no trouble, for 
purposes of comparison, may be noted 
on these drawings, or (if the drawings 
are crowded) listed separately. All 

supplementary information is also either 
noted on drawings, or filed as indicated. 
Envelopes or loose-leaf books contain- 
ing trouble data may in some cases be 
kept right inside the amplifier or other 
panel to which they refer. A much 
better method, provided they will not be 
lost, is to keep them handy for periodic 
refreshing of the memory. Data kept 
in mind are more quickly available than 
that kept on paper; but the written 
notes obviously should be ready at all 
times to make sure memory doesn't slip 
a cog. 

The Epoch of Progress in 
Film Fire Prevention 



The appended article is an abstract of an address delivered recently by Mr. 
Sulzer before the Greater New York Safety Council. The safety story of the mo- 
tion picture industry is a remarkable one, and to none more absorbing or im- 
portant than to projectionists who daily handle miles of film and whose 
interest in fire prevention grants precedence to none. Certain aspects of this 
article are discussed in an editorial which appears elsewhere in this issue. 

IT IS a privilege and an honor to be 
asked to present the story of the 
accomplishments in fire prevention in 
the motion picture industry. The East- 
man Kodak Co., having developed and 
introduced the flexible, transparent film 
that made the motion picture industry 
possible, and because of its long ex- 
perience in the manufacture of this film, 
is undoubtedly in the best position to 
outline this problem in its entirety. 

To understand the magnitude of the 
problem and the difficulties involved in 
fire prevention in the motion picture 
industry, we must go back to the be- 
ginning of the use of film in photography. 
In 1880, when Mr. Eastman began the 
manufacture of dry plates, he realized 
that photography could not be made 
popular with the average individual 
until something less bulky and less 
breakable than glass-plate negatives 
could be produced. 

In 1885 he first introduced stripping 
film, as it was called, which consisted 
of paper, coated first with a layer of 
soluble gelatin, then with a thin layer 
ol collodion (nitrocellulose), and finally 
with a coating of sensitized emulsion. 
The film was exposed by the photog- 
rapher, then sent back to the Company, 
where it was developed and laid emul- 
sion-side down on a glass plate. The 
soluble gelatin layer was then softened 
and the paper was stripped off, thus 
leaving a transparent negative on the 
glass plate for printing. 

Although this next development, strip- 

ping film, broadened the field of ama- 
teur photography considerably, Mr. 
Eastman realized that it was not the 
final answer. He therefore employed a 
chemist in 1886 to devote all of his time 
to the development of a suitable flexible, 
non-breakable, transparent material 
which could replace the paper of the 
stripping film and also serve as a 
permanent support for the sensitized 

Collodion, which is a solution of cellu- 
lose nitrate in ether and alcohol, had 
been used in wet-plate photography, the 
method that replaced the early Daguer- 
reotype process. It was the best-known 
and practically the only-known trans- 
parent material that would form itself 
into a continuous film when the solvents 
were evaporated. The film formed from 
collodion was found wanting, however, 
in many respects as a support for photo- 
graphic emulsions. 

Mr. Eastman was familiar with col- 
lodion from his experiments with wet- 
plate photography before he developed 
the Eastman gelatin dry plate with 
which he began his business career in 
photography. His later experiments in 
search of a transparent, flexible emul- 
sion-support demonstrated the unsuit- 
ability of collodion for this purpose. De- 
spite the defects of collodion, however, 
it was natural that the experimenter 
should concentrate on nitrocellulose, its 
main ingredient, in his search for a 
transparent, flexible support. After 3 
years of experiments, a formula of 

nitrocellulose and camphor in solution, 
suitable for negative support, was per- 
fected, and commercial production of 
nitrocellulose film base was started in 

• Properties of Nitr© Film 

Nitrocellulose is inflammable. Inflam- 
mability increases with the degree of 
nitration of the cellulose. Experiments 
demonstrated that, to produce a nitro- 
cellulose suitable for film support, a low 
degree of nitration must be maintained 
so that the resulting nitrocellulose would 
be less inflammable, less subject to de- 
composition, and of the correct solu- 

Nitrocellulose as used for photo- 
graphic purposes is not explosive, but 
is inflammable; and intelligent care 
must be exercised in its production, stor- 
age, and use. Nitrocellulose film base 
will not only burn rapidly when ignited, 
hut also, if subjected to sufficient heat, 
will decompose without flame. This 
film base contains enough combined 
oxygen to maintain decomposition when 
once started, even in a limited air sup- 
ply. Decomposition liberates compara- 
tively large quantities of carbon dioxide, 
carbon monoxide, and oxides of nitro- 
gen, which under certain conditions are 
dangerous to life. Some of these liber- 
ated gases are also inflammable, and 
under some conditions are explosive. 

Since decomposition, when once 
started, will maintain itself and generate 
enough heat to produce combustion, the 
obvious control, lies, not in methods in- 
tended to smother the fire by excluding 
the air supply, but by the application of 
large quantities of water sufficient ta 
cool the burning film below the decom- 
posing temperature of about 300 degrees 
F. Experiments demonstrated that such 
an application of water will also cool 
the liberated gases sufficiently to make 
explosion and even ignition, unlikely. 
This theory was followed in fire-protec- 
tion measures developed by the East- 
man Kodak Co., to which we will refer 

Nitrocellulose film was first used only 
in roll film for amateur photography. 
The development of equipment for the 
taking and subsequent projection of pic- 
tures which would seem to move had 
been waiting, however, for a flexible film. 
Therefore, almost immediately after 
Mr. Eastman announced the availability 
of flexible negative material, Thomas A. 
Edison, realizing that this was the an- 
swer to one of his most perplexing prob- 
lems, sent one of his men to Rochester 
to bring back samples with which 
he might carry on his experiments on 
motion picture cameras. Mr. Edison's 
first confirming order, covering a prior 
delivery of motion picture film, bears 
the date of Sept. 2, 1889. 

• First Commercial Shows 

Motion pictures first appeared com- 
mercially in peep shows in 1894. Then, 
on May 20, 1895, the first motion pic- 
lures were projected on a screen com- 
mercially, at 153 Broadway, New York 
City. This was a four-minute picture 
(Continued on page 21) 




SETTING new standards of quality and per- 
formance, Eastman's latest negative films 
have met with instant approval. Each makes 
its special contribution . . . fast, fine-grained 
Plus-X, for general studio work . . . high-speed 
Super-XX 7 for all difficult exposures . . . ultra- 
fine-grained Background-X, for backgrounds 
and all-round exterior work. All three offer 
the high reliability and photographic quality 
typical of Eastman sensitized materials. 
Eastman Kodak Company, Rochester, N. Y. 
(J. E. Brulatour, Inc., Distributors, Fort Lee, 
Chicago, Hollywood.) 

E ASTMAN Plus-X . . . 
Super-XX . . . Background-X 

APRIL 1939 11 

Enormous screen — 22 feet high and 187 feet long — on which are projected single panoramic views and groups of pictures 

Giant Twin Projectors Feature 
Novel Eastman Fair Exhibit 

THE scene is inside a huge building 
at New York's 1939 World's Fair in 
which is housed the exhibit which 
reflects the far-flung activities of the 
greatest photographic company in the 
world — Eastman Kodak. Passing through 
a dimly lighted foyer, the visitor enters 
the Great Hall of Color — a majestic, 
semi-circular room 65 feet in radius with 
a total area of 6500 sq. feet. Here he 
will see the most extraordinary photo- 
graphic pageant in history, which util- 
izes projection facilities hitherto un- 
dreamed of by even the most advanced 
practitioners of the art. 

An enormous screen — 22 feet high and 
187 feet long, extends along the entire 
inner circumference of the Great Hall. 
Along this screen, in single panoramic 
views and in groups of pictures, there 
passes the greatest show of color photog- 
raphy ever seen. 

• Continuous Color Projection 

Before the crowd's eyes, familiar 
scenes melt into places strange and far 
away. Time is condensed along with 
space as the world passes in review. 
Summer fades swiftly into winter, and 
just as swiftly back to summer again. 
In a few breaths, a majestic Western 
canyon scene changes from dawn to mid- 
morning, to noon, and declines through 
afternoon into night. Hundreds and thous- 
ands of pictures join in the kaleidoscopic 
march — pictures of people young and 
old, at work and at play — scenes of sun- 
shine and mist and twilight — flower gar- 
den and park and woodland — shimmer- 

ing blue water and skies rich with the 
glory of sunset. 

The screen is never dark. One 187- 
foot scene or group of scenes dissolves 
into the next, smoothly. Single pictures 
in groups of eleven are interspersed be- 
tween the panoramic views — and ail in 
rich, glowing color. 

It is a spectacle so dazzling as to be 
almost incredible. Even less credible to 

if IpBM 

Here are shown only the frame and 
lenses of one projector and, back of 
lens to the right, one of the lamphouses 
and heat filter. Weight, 2700 pounds 

many, will be the fact that these huge 
screen pictures are projected from small 
full-color transparencies little larger than 
a special delivery postage stamp. The 
interest of those who will view this spec- 
tacle will be divided between the color 
pageant and the mechanical ingenuity 
which makes such an exhibit possible — 
and this is where the projectors demand 

Each projector is a "twin" — two pro- 
jectors in one — and each weighs nearly 
a ton. Nearly as tall as a man, the pro- 
jectors bear no resemblance to conven- 
tional projection equipment. In them, 
each of two 45-inch steel drums carries 
96 color transparencies, firmly mounted 
on glass. Special gates and shutters are 
used for "fades" and "dissolves." 

• Use 11 Twin Projectors 

Eleven similar twin projectors are con- 
cealed in a spacious projection room just 
under the roof of the great hall. Through 
each of their gates stabs a brilliant beam 
of light. Tiny color-film transparencies, 
about 1 x 1/-2 inches, made on standard 
Kodachrome film, pass these gates — to 
become full-color screen pictures approx- 
imately 50,000 times as large in area! 
Each of the screen pictures is 17 feet 
wide and 22 feet tall, and eleven of them 
exactly fill the 187-foot screen. Inter- 
estingly, the transparencies which pro- 
duce these enormous pictures were made 
with cameras similar to those used by 
thousands of amateurs. 

As each small full-color transparency 
comes into position, it is registered in 



place to an accuracy of plus or minus 
1/10,000 inch, through a unique com- 
bination of optical and mechanical regis- 
tration. Moreover, this same registering 
system operates so that even while the 
transparency is in motion in the pro- 
jector gate, its enlarged image is held 
rock-steady on the screen. 

Each of the hidden projectors is syn- 
chronized with the others by an elaborate 
interlock — operating through a fully- 
automatic control system. To design 
them, and their operating system, in- 
volved hundreds of hours of planning 
and computation; and thousands of dol- 
lars went into their construction. 

Through its electrical interlock and 
control mechanism, the projection sys- 
tem can be operated with infinite flexi- 
bility. If desired, pictures can be changed 
at different speeds — one group of pic- 
tures remaining on the screen a half- 
minute, while others are changed up to 
four times a second. Fades, dissolves, 
motion effects can also be presented. 

Appropriately enough, the "heart" of 
the projection system control is a spe- 
cially notched sound-film, which not only 
carries the voice of a commentator and 
special musical accompaniment, but also 
regulates the movement of the projector 
shutters and the shifting of slides — keep- 
ing pictures and comment in perfect syn- 
chronism. With this special "index" 
film control, it is possible to start a cycle 
of the color show simply by throwing a 
switch- — and to halt all the projectors 
simultaneously just as simply. 

Designed by Eastman technicians, 
these projectors apply a wholly new 
principle to color-film projection. They 
are so adaptable that they can be used 
for any type of slide projection which 
calls for high magnifications. 

Huge fine-pitch ring spur gears are largest of type ever made. Each has 1440 
teeth. Color slides are bolted to these "drum" gears — 96 to each drum 

Employed in the Eastman projectors 
are the largest fine-pitch precision ring 
spur gears ever machined in the U. S. 
Each gear is 45 inches in diameter and 
carries 1440 teeth. On these "drum" 
gears are bolted glass-mounted Koda- 
chrome transparencies — 96 pictures to a 
drum. Twenty-two gears are used in the 
eleven twin projectors, so that the system 
carries 2,112 color-film pictures ready 
for automatic projection. 

To link the gear-sings with the auto- 
matic indexing system, the projectors 
employ one of the largest single-step 
spur gear reductions ever attempted — 48 
to 1. The 45-inch gears work directly 
from a 15/16-inch pinion. Each color 
slide carries a series of gear teeth, in- 
tegrally mounted along its edge. To- 
gether, these teeth form a continuous 
series around the film ring, and serve to 
operate the optical registering system 
built into each film gate. 

This registering means consists of a 
small rectangular plate of selected opti- 
cal glass, which spins as the film ring 

Optical registering device, a small plate of selected optical glass which spins as the 
film drum turns. Refraction effect can be observed. Slide is somewhat high in 
gate, but gears automatically tilt registering-plate forward, centering image precisely 

rotates. As each picture moves into 
position, this glass swings upright be- 
fore it. If the picture halts a trifle too 
high in the gate, the registering- glass re- 
mains tilted slightly forward at the top. 
If the picture stops too low in the, .gate,- 
the glass tilts back correspondingly, its 
movement being controlled by the gear 
teeth on the film. In either case, refrac- 
tion through the glass shifts the picture- 
image so that it travels at proper level 
through the lens, and is correctly posi- 
tioned on the screen. 

This correct level is maintained even if 
the color-slide vibrates up and down in 
stopping, since the registering glass 
moves in synchronism with it. Such a 
means of optical registration has here- 
tofore been found only on ultra-speed 
laboratory cameras, used for taking pic- 
tures at 1/100,000 to 1/500,000 second; 
but in the Kodak Building projectors, it 
helps provide screen registration of un- 
paralleled accuracy. 

The illuminating system of each pro- 
jector is centrally housed, with the ring 
gears and file drums revolving around 
it. Water cells are used for cooling, and 
hi addition, a blast of air, chilled almost 
to freezing, is directed on each projector 
gate. Large-aperture, long-focus projec- 
tion lenses are used, and specially de- 
signed shutters are utilized. 

Eastman prepared a special collection 
of more than 100,000 Kodachrome trans- 
parencies. The design of the Kodak pro- 
jectors makes it possible to change the 
whole color show overnight, simply by 
unbolting one group of slides, and re- 
placing them with another. Pictures 
will be shown continuously from 10 P.M. 
each individual show lasting approxi- 
mately twelve minutes and utilizing more 
than 2000 full-color slides. 

The tiny full-color slides used in pro- 
jection are identical with those any ama- 
teur can make today with a miniature 
camera. They were made on the same 
types of Kodachrome Film the amateur 
uses, are the same size, and — if re- 
mounted as regular 2 x 2-inch slides — 
could be shown in any inexpensive home 

APRIL 1939 


3 amp. rtt 

S-l j 






Seventh Subscription Contest Diagram 

LAST month's Contest diagram (Fig. 
1), although comparatively easy, 
netted only ten winners out of an ex- 
tremely large number of contestants. 
Many more entries would have scored ex- 
cept for two oversights committed by an 
astonishing number of contestants who 
otherwise turned in first-rate replies. Not 
a few men failed to note the obviously 
low value of the plate resistance of Tube 
No. 1. Similarly, many contestants failed 
to see that Tube No. 6 screen grid was 
grounded to shell — which is surprising, 
indeed, since the other three 6L6 tubes 
offered a perfect basis for comparison. 

Those who scored in last month's con- 
test follow: H. D. Taylor, Raleigh, N. C. ; 
V. H. Brant, Conway, Ark.; Fred Snod- 
grass, New Martinsville, W. Va. ; Herman 
Polies, Miami, Fla.; Paul Meilink, San- 
dusky. Ohio; E. J. Doolittle, Baltimore, 
Md.; C. H. Siddall, Azusa, Calif.; B. G. 
London. Stamford, Conn., and R. W. 
Rushworth, Baltimore, Md. 

There were two other successful con- 
testants who will receive no credit for 
their efforts because of the oft-repeated 
rule requiring that all entrants be sub- 
scribers to I. P. No consideration will 
be extended to replies received from non- 

The changes made in the March dia- 
gram were: 

Connection dot added where the recti- 
fier filament jumper crosses the ground 

Connection dot added between No. 2 
grid line and line running to the right 
from C-6. 

Section of wire removed between the 
ground bus and the connection running 
to the right from R-8, R-7 to the lower 
end of C-7. 

Plate load of No. 1 tube changed from 
82,000 ohms to 200 ohms (R-4) . 


Short added between the right side of 
R-3 and the screen grid line. 

No. 6 screen grid grounded to No. 6 
shell by addition of dot. 

lupur com. 
oieecT to .. 
cojjd. o-\\ 

This month's Contest offering (Fig. 2) 
presents no particular difficulty to those 
projectionists who know their circuits 
and who are able to painstakingly trace 
them through. As is customary, practi- 
cally the entire circuit has been redrawn, 
so it is useless to attempt thus to check 
upon the changes made. The usual rules 
will prevail: only subscribers to I. P. are 
eligible to compete ; and all answers must 
reach I. P. not later than May 22. 

It is not necessary to enclose a copy 
of the diagram in order to receive con- 
sideration. Simply list the errors found, 
append your name and address, and mail 
to I. P. 

Simplex Adds E System to 
Reproducer Line 

Supplementing its present line ot 
sound reproducers, International Projec- 
tor Corp. has just announced a new 
Simplex E reproducing system designed 
expressly for small theatres. The system 
differs radically from other 4-star models 
only in the matter of power, its output 
being 10 watts. The motor and sound- 
head are unchanged, there is only one 
volume control, and there has been some 
slight modification in speaker equipment. 
Dividing mark for low- and high-fre- 
queny is 800 cycles, this figure being 
adjudged best for small auditoria. 


(85 V) 


Hit puitb 


CHOuGEOvee t / 


Power Pack 


CMkiGEOvee *z. 


C(*.C1. » l) 







„C (*CA*Z) 

FIGURE 2. Volume Control Amplifier 


An Analysis of Light: Terminology 
and Procedure in Plotting Curves 


IN THE technical discussion of light 
it is frequently necessary to define 
the characteristics of radiation from 
a given source in exact terms. To 
understand the meaning of such defini- 
tion it is essential that one have knowl- 
edge of the generally accepted theory of 
light radiation. 

Light is known to be far more complex 
than it appears to the human eye. The 
eye cannot separate a beam of light into 
separate components of different colors. 
It sees only the resultant effect of all 
colors that may be present. Yet, by 
passing a beam of white light from any 
source through a prism, a piece of glass 
or quartz of blunt wedge shape, it can 
be spread out into a band of brilliant 
color ranging from red through orange, 
yellow, green, blue and violet. This sep- 
aration of light into its component parts 
is called a spectrum. The rainbow is the 
spectrum of sunlight refracted through 
the raindrops upon which it falls. 

Another shortcoming of the human eye 
is that it does not respond to all of the 
spectrum spread out before it by means 
of the prism or that other more accurals 
optical device known as the diffraction 
grating. It has been known for a long 
time that sunlight includes radiations be- 
yond the red portion of the spectrum but 
invisible to our eyes. These have been 
termed the infra-red or heat rays. Invisi- 
ble rays at the opposite end of the spec- 
trum have also been discovered. These 

Vitally important to a thorough under- 
standing of the projection art is a 
knowledge of tight, its composition and 
action, and this in turn requires a famil- 
iarity with the terminology employed 
by those who work with light. This 
need is filled, and admirably so, by the 
accompanying article, which merits most 
earnest consideration by every projec- 

are called ultra-violet, that is, beyond the 

While light rays can be referred to as 
ultra-violet, luminous (visible) or infra- 
red and the luminous rays further identi- 
fied by color sensation produced on the 
eye, it is often desirable to define a par- 
ticular ray or band of rays more specifi- 
cally. It is known that light has many 
of the properties of a vibration or wave- 
motion. These waves are much like the 
ripples which spread from a point where 
a stone has just been dropped into a 
quiet pool. 

• The Visual Spectrum 

There is a tremendous difference, how- 
ever, in the speed with which the light 
waves travel as compared with the waves 
of water. Light waves travel at a speed 
of approximately 186,000 miles, or 300,- 
000,000, meters per second, which means 
that the time required for light to travel 
the 93,000.000 miles from the sun to the 
earth is about 8 1/3 minutes. 

Light waves are part of the same fam- 
ily which includes radio waves, infra- 
red waves, ultra-violet waves, X-rays, etc. 
Fig. 1 shows a chart illustrating the re- 
lationship of all these various waves to 
those which go to make up the visual 
spectrum. So far as we know, the speed 
and fundamental nature of all the waves 
in this series are identical. They differ, 
however, in their frequencies and wave- 
lengths. By frequency we mean the 
number of complete waves or cycles pass- 
ing a given point in one second; and by 
wave-length we mean the distance be- 
tween the successive wave crests. 

Let us analyze for a moment the radio 
broadcast band shown in Fig. 1. We 
see that this band includes radiations 
with wave-lengths which range between 
200 and 545 meters. The frequency with 
which these wave-lengths pass a given 
antenna is obtained by dividing the vel- 
ocity (300,000,000 meters) by the wave- 
length in meters or 

Velocity -s- Wavelength = Frequency 

For wave-lengths of 200 meters the 
frequency is 1,500,000 waves or cycles 
per second, and for wave-lengths of 545 
meters the frequency is 550,000 cycles 
per second. These frequencies are m:>re 
commonly expressed in kilo-cycles. One 
kilo-cycle is equivalent to 1,000 cycles. 
Expressed as such, these two frequencies 
are 1500 and 550 kilo-cycles per second, 
respectively. We are familiar with these 
terms, as they represent the divisions 

aOjDOO 545 200 10 I 







0.1 1 100.000 


400 100 




-L_l l i 

1.4 .06 












I WITH--' 




— REP- 






5860 5350 A920 



422Q 4000 

APRIL 1939 


1 Micron = 1/1,000,000 meter 

1 Millimicron (a unit often used) = 1/1,000 micron 

1 Angstrom Unit = 1/10 millimicron; 1/10,000 micron; 1/10,000,- 

000,000 meter 
1 Angstrom Unit equals about four billionths of an inch 
10 Angstrom Units = 1 millimicron 
10.000 Angstrom Units = 1 micron 


commonly used on the dials of our radio 

A little further analysis of the wave- 
lengths used for radio communication 
outside of the regular broadcast range 
shows that these waves range from 0.1 
meter (4 inches) to 30,000 meters (20 
miles) in length. The corresponding 
frequencies for these two extremes are 
3,000,000 kilo-cycles and 10 kilo-cycles 
respectively. In dealing with these high- 
er frequencies the term mega-cycles is 
generally used. A mega-cycle is equal 
to 1,000 kilo-cycles or 1,000,000 cycles. 
For instance, the 3,000,000 kilo-cycles 
mentioned above can also be expressed 
as 3,000 mega-cycles. 

A further analysis of the Radiation 
Spectrum (Fig. 1) reveals that the vari- 
ous wave-lengths shown are expressed in 
three different units namely meters, mic- 
rons, and Angstrom Units. These units 
all bear a decimal relationship to the 
meter, as shown in Table A. 

• Definitive Units 

It is evident from these figures that 
the wave-lengths shorter than those in 
the radio band are extremely short and 
the frequencies are so high that it is not 
convenient to express them in everyday 
units. For this reason the physicists 
have adopted the units shown in Table 
A. This permits definition of wave- 
lengths in integral values instead of 
cumbersome fractions. It is also true, 
in dealing with the Radiation Spectrum 
beyond the radio bands, that the fre- 
quency nomenclature is seldom used. 

As shown by the previous equation, a 
fixed relationship exists between fre- 
quency and wave-length, so that a com- 
plete specification is provided by the 
use of either one of these terms alone. 
The Angstrom Unit is the (one most 
commonly applied by physicists to that 
part of the Radiation Spectrum defined 
as ultra-violet, visible and infra-red. This 
unit bears the name of the Swedish physi- 
cist Angstrom. 

It will be noted that the region of the 
Radiation Spectrum covering the range 
of visual light extends from 4,000 to 
7,000 Angstrom Units. This narrow 
band of radiation is of very great import- 
ance because the human eye is responsive 
to radiation of wave-lengths within this 
range. It will also be noted that this 
region is immediately bounded by infra- 
red rays (heat rays) on one side and by 

ultra-violet rays on the other side, neither 
of which rays are visible to the human 

Other than the fact that the human eye 
is stimulated by the visible rays, these 
rays are the same in general character 
as those on either side. The wave-lengths 
in these adjacent bands are such that it 
is convenient for us to apply the same 
unit of measurement in defining them. 

The visual spectrum (4,000 to 7,000 
Angstrom Units) has been enlarged in 
the lower part of Fig. 1 to show the re- 
lationiship of the various colors of light 
of which it is composed. A sensation of 
red is produced when radiation of wave- 
lengths from 6470 to 7000 Angstrom 
Units strikes the eye. Likewise a sensa- 









h (P 




S J0 



oo <y 

» 50 

90 5< 





a 70 




tion of orange is produced by wave- 
lengths of from 5860 to 6470 Angstrom 
Units. Shorter wave-lengths stimulate 
other color sensations such as yellow, 
green, blue and violet. Table B sum- 
marizes this information with wave- 
length and frequency specifications in a 
variety of units. 

These color divisions of the spectrum 
are only approximate. Each color shades 
by imperceptible degrees into the next 
one and we cannot say definitely where 
orange ends and red begins. We can de- 
fine color exactly, however, by placing 
Angstrom's scale of wave-lengths be- 
side the spectrum and noting the num- 

ber that corresponds to the particular 
color in question. 

When we speak of radiation of so 
many Angstrom Units we define the 
position of that particular ray of light 
in the spectrum, whether it be in the 
ultra-violet, visual, or infra-red region. 
The description means the same thing 
to everyone familiar with the Angstrom. 
Unit scale. 

We have mentioned previously that 
the human eye does not respond equally 
to all wave-lengths. If the eye were 
subjected in turn to radiation of a num- 
ber of wave-lengths over the visual range,, 
all of equal energy value, the relative 
response would be indicated by the fam- 
iliar visibility curve, Fig. 2. This curve 
shows that the eye is most efficient at a 
wave-length of 5,500 Angstrom Units. 

The same amount of energy at wave- 
lengths of 5,100 AU or 6,100 AU pro- 
duces only half as much visual response; 
while at 4,000 AU and 7,000 AU the 
response of the average human eye is 
practically zero. Actually the average 
response at 4,000 AU is 0.009 percent 
of that at 5,500 AU, and at 7,000 AU it 
is 0.3 percent. This is also another way 
of saying that different color sensations 
are stimulated to different degrees when 
light or different wave-lengths strikes 
the eye. However, if radiation of all 
wave-lengths between 4000 and 7000 
Angstrom Units is present in substan- 
tially equal amounts, then no one color 
predominates and we say that the light 
is white. This is an important point to 
remember in the discussion which fol- 

• Plotting Light Curves 

By means of an instrument known as 
the spectroscope it is possible to show 
the spectrum of any light source, either 
natural or artificial, and with the further 
aid of sensitive detecting instruments 
such as thermopile, the photo-electric cell 
and the photographic plate, study the 
characteristics of the given light source 
from a quantitative as well as a quali- 
tative point of view. It was by this 
method that the Spectral Energy distribu- 
tion curves of the light from the National 
SRA and National Suprex carbons shown 
in Figs. 3 and 4 were obtained. 

These curves show the distribution of 
energy from these two light sources from 



Wave-Length Range 

Frequency Range 







of an Inch 

of Cycles 




































51 » 






3SOO 4000 

SOOO 6000 




Spectral energy distribution curve, "National" SRA carbon 

arc: 12 mm. positive, 8 mm. negative; 30 amps., 58 volts 

d.c. at the arc. 

3500 4000 


5000 feOOO 


Spectral energy distribution curve, "National" Suprex car- 
bon arc: 7 mm. positive, 6 mm. negative; 50 amps., 36 
volts d.c. at the arc. 

the near ultra-violet throughout the vis- 
ual range of the spectrum. The intensity 
of radiation for any given wave-length 
on the Angstrom Unit scale is shown by 
the vertical height of the curve at that 

Both curves were made at the normal 
operating currents and voltages for these 
two types of arcs as used for motion 
picture projection, namely, 30 amperes 
and 58 volts for the 12 mm. x 8 mm. 
SRA arc, and 50 amperes and 36 volts 
for the 7 mm. x 6 mm. Suprex arc. The 
arc wattage for both of these light 
sources is practically the same, namely, 
1740 watts for the SRA arc and 1800 
watts for the Suprex arc. 

It is possible, therefore, to make some 
very interesting comparisons between 
these two light sources by means of 
these spectral energy distribution curves. 
The curve for the SRA low-intensity arc 
shows clearly the greatest amount of 


Labor, firmly intrenched at the N. Y. 
World's Fair, has participated in some fancy 
jurisdictional battles over work allotments, 
the chief brawl being among I. A. and 
I.B.E.W. units. Latter group, having done 
the original electrical work on numerous 
exhibits, utilized every device to keep its 
men on the job when the exhibits opened 
to the public. I. A. units consider all ex- 
hibits as "shows," thus theatrical ventures, 
and insist upon jurisdiction. 

Many such differences existed right up to 
opening day of Fair. Moreover, the two 
I. A. stagehand units in Brooklyn and N. Y. 
staged a few tiffs themselves relative to 
transport, erection and handling of scenery. 

N. Y. pojectionist union Local 306 ex- 
pects to have at least 100 men working on 
the Fair grounds. General rule is one man 
to each projector operating, whether 35 or 
16 mm., while the automatic continuous pro- 
jectors are assigned one man to a group of 
about eight machines. Many projection 
manpower details not yet settled. 

energy is concentiated in the yellow, 
orange and red end of the spectrum, 
with less energy in the violet, blue and 
green, and, further, that the distribution 
of this energy varies in increasing quant- 
ities throughout the visual spectrum 
(4,000 to 7,000 AU) as indicated by the 
shape of the curve. 

The curve of the Suprex high intensity 
arc, however, shows a much more even 
distribution of energy throughout the 

visual spectrum with considerably less- 
energy in the orange and red than is- 
evident in the SRA arc. This difference 
in energy distribution explains clearly 
the reason for the yellowish tint of the 
screen light from the low-intensity arc. 
It also explains the daylight quality of 
the Suprex arc, which is the direct result 
of the very even distribution of the en- 
ergy and corresponds to the definition 
previously given for white light. 

I. A. Coast Autonomy Battle; N. Y. City Strike Illegal, 
Opines D. of J. ; Receiver for St. Louis Union 

DEVELOPMENTS on the labor front 
were many and interesting during 
the past month. In Hollywood, the so- 
called autonomy group within Local 37 
gave battle on a wide front to the I. A. 
General Office in an effort to oust the 
latter from control of the Union. I. A. 
recently granted local autonomy to Local 
37, only to again assume control a few 
weeks later after ousting the elected 

I. A. contends that its Local 37 oppon- 
ents are dominated by Communists, a 
charge that is now being investigated by 
the Dies Committee. The autonomy 
group, in a series of sensational affidavits 
filed in the courts, contends that I. A. 
seeks control of the studio unions as a 
means of extending its centralized power. 
Peace seemed assured at one stage of 
the proceedings when I. A. agreed to 
restore autonomy and permit direct nego- 
tiation on scales and conditions between 
Local 37 and the producers, with the 
proviso, however, that the I. A. drive 
for the expulsion of "subversive" influ- 
ences within Local 37 would not cease. 
The proposed peace pact blew up in the 
face of a series of demands by the auton- 
omy group. 

The latest development in the studio 

mess was the announcement by the au- 
tonomy group that it would campaign to- 
have all I. A. studio members refuse ta 
pay dues to the International — -pending 
withdrawal of I. A. officials. The General 
Office scoffed at this announcement and 
reiterated its determination to "clean up'* 
the Coast situation. 

Further complicating the situation was 
the refusal of the producers to negotiate 
with I. A. Coast unions under the terms 
of the Basic Wage Agreement, formu- 
lated some years ago. The General 
Office forced the producers to capitulate 
by wiring a stand-by strike order to all 
affiliated locals. Negotiations are ex- 
pected to begin shortly. 

# D. of J. Intervenes 

The conflict between the General Office 
and Local 37 has been the topic of al- 
most daily releases over press association 
wires. This fact, plus developments in 
the N. Y. Loqal 306 strike against the 
film exchanges, claimed the attention of 
the Department of Justice, which an- 
nounced that it would investigate all 
angles of the I. A. situation to determine 
whether there had been any violation of 
the anti-trust statutes — the theory evi- 

APRIL 1939 


dently being that I. A. activities were 
impeding interstate commerce. 

The strike by Local 306 in New York 
City against the major film exchanges 
and laboratories came to an abrupt end 
upon announcement by the Department 
of Justice that it considered illegal the 
methods employed by the Union in at- 
tempting to force distributors to refuse 
film service to 75 theatres which use 
other than 306 projectionists. Precisely 
this result was forecast in I. P. last 

Although failing in its main objective, 
Local 306 succeeded in obtaining a sub- 
stantial wage increase for its exchange 
projectionists, retroactive to Sept. 1, 
1938 and running until Sept. 1, 1940. 

In St. Louis, the Circuit Court, acting 
upon a petition signed by 66 members of 
Local 143, appointed a receiver for the 
Union and issued a sweeping injunction 
barring all interference by the I. A. Gen- 
eral Office in the operation of the Union 
and in control over Local members. The 
Union has been under I. A. supervision 
for several years. 

The Local 143 receivership, similar in 
many respects to the Local 306 receiver- 
ship of six years ago which was speedily 
voided by a higher court, is notable in 
that the receiver named is distinguished 
chiefly for his anti-union attitude and 
activities in the industrial concern which 
he heads. 

Pittsburgh Local 171 has voted to re- 
tain General Office supervision over its 
affairs for the next two years. 

Mass. 'Safety' Bill Killed By 
Union Opposition 

The death blow to Mass. Senate Bill 
241, relating to a projector "safety" de- 
vice that has worried New England pro- 
jectionists, was delivered by Thad Bar- 
rows, president of Boston Local 182, at 
a recent legislative hearing. Similar 
bills still are being studied by legislative 
committees in Maine and in New Hamp- 

In opposing the bill, a description of 
which is appended hereto, Barrows 
pointed out that the device mentioned 
therein was not patented, seemingly be- 
cause of its close similarity to another 
device known as the Coda, and that in 
his opinion it not only did not afford 
the protection claimed but in fact intro- 
duced additional hazards to the projec- 
tion process. Barrow stated that the 
record of the Mass. Dept. of Public 
Safety in supervising projection appara- 
tus in itself rendered unnecessary use of 
the device. 

Pertinent portions of the bill follow: 

No cinematograph or other apparatus, 
hereinafter in this section called the ma- 
chine, involving the use of an inflammable 
film or projection record, shall be used for 
the purpose of exhibiting such film or rec- 
ord in any place where an audience or col- 
lection of persons is assembled to witness 
said exhibition unles the machine is equip- 

Important Notice! 

The management of INTERNA- 
to acquaint its readers and adver- 
tisers with the fact that this paper, 
unlike certain other publications, 
holds not one share of stock of, 
nor has any special interest in, any 
company manufacturing motion pic- 
ture theatre equipment. I. P. ac- 
cepts advertisements on a cash basis 
only, and it believes that the accep- 
tance of stock or any remuneration 
other than cash in payment for ad- 
vertising is unfair to its readers 
and, doubly so, to its advertisers. 

Also, the ownership of I. P. is 
vested solely in two persons who are 
active in its operation, and it does 
not owe a nickel to any bank or 
manufacturing company. 

ped or fitted with a safety control device 
that will automatically interpose an opaque 
heat-resisting shutter or guard between the 
projection light and said film or projection 
record instantaneously on the breaking of 
the said film or record, due to burning or 
other cause on the stopping of the move- 
ment of said film or record through the 
path of said light, or on any interruption 
of or change of the regular feed movement 
of said film or record through said path 
of light from that required by the regular 
operation of the machine due either to fire 
or defect in said film or record or in the 
operating mechanism of the machine, or 
from other causes, and that will instantly 

shut off the motive power of the machine 
and stop its moving mechanism. 

Said safety control device shall be free 
from a multiplicity of contact controls in 
order to reduce congestion of parts with 
consequent possibility of mishap and con- 
fusion and shall, in the case of a picture 
projection machine or device, comprise a 
single control unit operated by the moving 
film or record and, in the case of a com- 
bined picture projection and sound repro- 
ducing machine, comprise not more than 
two such control units, one for the picture 
projection mechanism and the other for 
the sound mechanism. 

H.T. Matthews Heads Motiograph, 
Succeeding J. B. Kleckner 

H. T. Matthews has been named pres- 
ident and general manager of Motio- 
graph, Inc., succeeding Joseph B. Kleck- 
ner, who resigned recently. Matthews 
has been secretary of Motiograph for 
the past two years. 

Matthews stated that the management 
shift would not involve any alteration of 
the company's policies or operation. "We 
contemplate no other executive changes, 
either in the sales or manufacturing de- 
partments; and there will be no major 
change in common holdings of the com- 
pany," he said. 


Neighborhood Theatres, Inc., of Richmond, 
Va., has signed for Altec service for all its 
21 theatres. The Rome Circuit, Baltimore, 
Md., has also signed with Altec for 14 

Proper Viewing of Motion Pictures 



THE problem of proper viewing of 
the motion picture is a more com- 
plex one than is supposed on first 
thought. The more common seeing 
problems of everyday life have only re- 
cently been dealt with fairly success- 
fully, and the work done in this field 
can be used as a guide in the motion 
picture viewing problem. Yet this 
problem differs from the common seeing 
problem inasmuch as a great number of 
people view a given motion picture at 
one time, while the common seeing prob- 
lems involve usually only one person in 
a reading or working task. 

Actually, there is a limited number of 
people who can properly see a screen 
image at one time. This number will 
vary with the size and lighting of the 
screen image and the efficiency of the 
seating arrangement. For example, an 
incorrectly sized and illuminated screen 
image and an inefficient seating arrange- 
ment will greatly reduce the number of 
people who can properly see the picture. 
And so there may be a thousand seats in 
a given theatre, but only half that amount 

may afford satisfactory viewing of the 

The absolute maximum number of 
people who can properly see a motion 
picture image at one time is controlled 
by the maximum advisable magnification 
of the 35 mm. film and the amount of 
screen illumination available. The Pro- 
jection Practice Committee of the 
S.M.P.E. conducted a study survey of 
about 600 theatres which indicated this 
maximum to be about 2,000 people. 

• Good Viewing Maximum 

The important problem is not so much 
to solve how large a capacity can be 
developed in any theatre as it is to 
arrange for a thousand good seeing posi- 
tions where a thousand seats are in- 
stalled, if such a thing be possible. The 
average theatre presents no such favor- 
able circumstances. In many instances, 
as much as thirty per cent or more of 
the seating capacity affords poor seeing 

Poor seeing conditions may constitute 
physical discomfort or fatigue, the in- 
(Continued on page 20) 





Vol. 14, No. 4 


APRIL 1939 

Fire Prevention Elsewhere in this issue there 

in the Theatre a ™ ea ™ a " abstraCt ?! an f" 
tremely interesting address de- 

Non-Existent Hvered recently by Mr. Alfred F. 
Sulzer, vice-president of Eastman 
Kodak Company, before the Greater New York Safety 
Council. Mr. Sulzer's topic is film fire prevention in the 
motion picture industry; and we can think of no subject 
of more absorbing interest to motion picture projection- 
ists than this; nor do we know of anybody more emi- 
nently qualified to discuss this topic than Mr. Sulzer. 
A careful reading of this article (which course we recom- 
mend to every projectionist) reveals certain statements 
which seem to call for a bit of editorial comment. 

Nobody can deny that the motion picture industry and 
the various underwriting companies have done a mag- 
nificent job in overseeing the handling of film. Every 
step of the journey of film stock, from manufacturer to 
delivery at the theatre, is hedged with safeguards such 
as are unsurpassed in any other industry. Studios and 
laboratories handle film with extreme care born out of 
a great respect for the potential powers for damage in- 
herent in such a product. Film exchanges have compiled 
such a formidable record for safe handling of film as to 
render superfluous any extended comment thereon. But 
what about the handling of film in theatres? 

Mr. Sulzer refers to "the practical absence of fires in 
motion picture theatres"; and he comments on the "negli- 
gible number of fires (in the film industry) as compared 
with the number attributable to any other cause." Both 
statements are beyond criticism — if we fix firmly in our 
minds the fact that Mr. Sulzer speaks from the viewpoint 
of a manufacturer the extensive distribution of whose 
product is vitally dependent upon rigid adherence to the 
rules of safety. 

We in the projection field look upon statistics of com- 
parable performances much less complacently than do 
other industry workers; and we would be willing to ac- 
cept something a bit short of perfection. "Comparable" 
looms as a gigantic word to us when we recall the hun- 
dreds of projection room fires which occurred during 1938 
and the score or more projectionists who lost their lives 
as a result thereof. True, included among the "hundreds" 
of such fires were numerous small blazes that were confined 
to a few seconds duration in the projector head; but these 
circumstances can neither erase them from the tally sheet 
nor minimize their potential power to kill humans and 
destroy property. We in the theatre will instinctively ask 
ourselves : "Just what do all these elaborate safety measures 
mean to us in the theatre?" A moment's sober reflection 
must inevitably bring the answer: "Nothing". 

Where the degree of precaution should be highest in the 
theatre, it actually is the lowest. Strange it is that the 
moment a print is developed to a theatre the whole elabor- 

ate safety system that has been so painstakingly built up 
collapses. Oh, yes, we are aware of the work of national, 
state and local regulatory bodies in throwing safeguards 
around moviegoers; we are familiar with the various 
codes relating to various types of structures, forms of 
construction, placement of exits, etc. But none of these 
activities goes to the core of the problem — which is the 
motion picture projector itself and its state of repair or 
disrepair. Certainly there is a streak of carelessness in 
all of us, particularly when executing familiar tasks; but 
the number of theatre film fires due to projectionist negli- 
gence is as nothing compared with the number of fires 
occasioned by worn and defective equipment — setting aside 
all consideration of the screen image. 

On a recent trip through eight states we had occasion 
to visit many projection rooms, wherein we examined 
carefully the projectors. The condition of some of these 
projectors was, and undoubtedly still is, such as to defy 
description — and if we were to essay this task, we should 
be accused of gross exaggeration. But if one can imagine 
taped moving parts! one can get an idea of the long list 
of lesser shortcomings. Worn sprocket teeth were com- 
monplace, and so worn as to occasion wonder that they 
could possibly engage the film. But we're not listing 
projector defects herein; we're trying to make a point. 
What is it? Just this: why not supervision by the under- 
writers or some national regulatory body over the physical 
condition of the projector? 

Projectionists and a relatively few progressive managers 
have for years preached the doctrine of projector repair 
and replacement, not only on the score of safety but also 
because of pride in a good screen image. But the efforts 
of this group of sensible people have gone for naught inso- 
far as impressing the great majority of managers is con- 
cerned. The latter will toe the mark only if forced to do 
so. That force can come only from one source, already 

Projectionists should continue to battle strenuously for 
repairs and for replacement parts. If the boss has little 
regard for the quality of the screen image, he should be 
reminded that the projectionist has more than a slight 
interest in his personal safety. Without this continuing 
struggle by projectionists to effect improvement in equip- 
ment repairs and replacements, the list of film fire 
tragedies would be many times its present total. Pro- 
jectionists should keep eternally after the boss on this 
topic, blasting away at every opportunity. 0. K., let it 
be for purely selfish reasons. 

Yes, we agree with Mr. Sulzer that the fire prevention 
record of the motion picture industry is indeed a remark- 
able one — that is, up to the point of delivery of the film 
to theatres. Beyond this point fire prevention not only 
does not exist but is not even considered. And it never 
(Continued at foot of next page) 

APRIL 1939 


Proper Viewing of Motion Pictures 

(Continued from page 18) 

ability to discern important detail im- 
ages on the picture, or the appearance 
of a distorted screen image. These are 
the definite undesirable seeing con- 
ditions which may exist; but there are 
additional poor seeing conditions which 
.may be considered less definite or more 
difficult to discern. 

These latter conditions deal with the 
relationship of the appearance of the 
.screen image to the appearance of the 
physical surroundings of the screen, and 
the lighting effect surrounding the 
.screen image. Although the latter con- 
ditions are not seemingly objectionable 
when incorrectly treated, there would be 
jnore artistic and less fatiguing effects 
obtained if the treatment were correct, 
and therefore prove to add greatly to 
the general dramatic effectiveness of the 
screen presentation. 

Yet it is important at this time to at 
least correct the more definite and ob- 
jectionable poor seeing conditions, and 
hope that further improvements will fol- 
low soon. The first of the important see- 
ing conditions to be considered is that of 
the ability of the viewer to see the en- 
tire picture without having to con- 
stantly shift or raise the position of his 
head to overcome the obstruction of the 
"view of the picture caused by the person 
seated in front of him. The expression 
"sight-lines" is often wrongly used in 
connection with this problem, because 
this expression covers another seeing 
consideration, that of the viewing angle. 
And so this first consideration should be 
thought of separately as the "screen 
obstruction problem." 

• Conventional Floor Slope 

The older and common method of 
•dealing with this obstruction problem 
in the past has been to rely upon slop- 
ing the orchestra floor downward to- 
ward the screen supposedly so that any 
person would be seated high enough 
above the person in front so that the 
person in front would not cover the 

screen image, partially or wholly. This 
method proves satisfactory in theatres 
having no more than approximately 
eighteen rows of seats in depth, but does 
not work out so well in theatres of 
greater depth, because the amount that 
the floor would have to slope would 
become too excessive for practical use. 

For example, a pitch from one row 
back to another row in the first few 
rows near the screen for obtaining 
proper clearances may have to be about 
% inch, whereas the pitch from the 
30th to the 31st row may have to be 
about 4 inches. This need for a greater 
rise per row as the number of rows from 
the screen becomes greater necessitates 
the excessive floor pitches. 

For want of a better solution or lack 
of study, theatre designers in the past 
followed the least line of resistance by 
avoiding the highly impractical steep 
floor pitches and therefore used a com- 
promise floor slope which would not be 
too great. To make matters worse, they 
found a good excuse for the compromise 
floor slope by claiming that "second- 
row vision" was achieved. Many of the 
well known theatre architects still are 
designing new theatres in which the 
floor slope and seating arrangement 
provide for "second-row vision." The 
full meaning of this so called "second- 
row vision" should be made clear to you, 
and then you should use your own judg- 
ment as to whether or not you will con- 
sider it a solution to the screen obstruc- 
tion problem. 

The technical explanation of the term 
"second-row vision" is as follows: A 
person seated in a given seat could see 
the entire screen over the head of a 
person seated directly in front but two 
rows ahead. Therefore, if there is no 
person seated directly in front and in 
the row immediately ahead, this con- 
dition should prove satisfactory. 

But, fortunately, for the exhibitor, and 
unfortunately in the case of this seeing 
solution, there is usually somebody 

seated in the row immediately ahead and 
directly in front. Then, under such con- 
ditions, how does a person manage to 
see the screen when there is someone 
seated immediately in front? To see 
the picture, you will find the viewer 
hugging up against one of the arm 
blocks of the chair and cocking his head 
to one side so that the head of the 
person in front will not be in the way. 
And then if a person in any of the rows 
ahead decides to move, everybody in the 
line has to shift again to gain a view 
of the screen, and in the shifting time 
miss some of the action of the picture 
and of course break the continuity. 

If the viewer wants to sit comfortably 
with the bulk of his weight centered 
over the seat of the chair and remain 
in any desired position without having 
to shift his position constantly, he just 
won't see the screen. 

• Reversed Slope Plan 

There is no doubt that seeing a mo- 
tion picture should prove more enjoy- 
able if the viewer does not constantly 
have to maneuver the position of his 
head and body to gain a view of the 
screen. New methods of floor slope de- 
sign and seating arrangement make it 
possible to achieve "first-row vision," 
which is meant to indicate that the 
viewer can, regardless of the posture 
he assumes, at all times see the screen 
over the head of the person immediately 
in front and in the row ahead as well 
as? over the heads of persons in all other 

Every projectionist should observe the 
viewing conditions in his theatre and 
report to his superior the existence of 
faulty conditions, because such con- 
ditions can be rectified even in exist- 
ing structures. The objectionable screen 
obstruction here discussed is to be 
found chiefly in the seating area of the 
main floor and upper levels of seating, 
starting with about the twelfth row from 
the screen, and in the center section of 
seats covering a width which would be 
equal to about the width of the screen. 
Since the seating area described is the 
choice seating area for viewing motion 
pictures, it is important that the obstruc- 


(Continued from preceding page) 

will be until such time as force is employed to whip into 
line those managers who run their projectors to death and 
thus cheat the paying audience and threaten their very 

The entire motion picture industry is concerned in this 
matter, because it would require only a couple of "unlucky 
breaks", a very few "unpleasant incidents", to cause the 
regulatory bodies to swing into action and revise the whole 
setup relating to the handling of film. At the present 

moment fire prevention in theatre projection rooms is a 
joke; it doesn't exist. We believe that the solution to 
this problem lies in voiding the discretionary powers over 
projection equipment now lodged in the managers (most 
of whom don't know the difference between a sprocket and 
a lens holder) and transferring it to a national regulatory 
body. Then, and then only, will we get action on this 

Fire prevention in the theatre today hangs by the slender 
thread of constant projectionist insistence and dogged per- 
sistence. May these efforts never cease. 



tion problem be properly disposed of for 
these seats. 

In a later article I will discuss other 
problems of proper seeing of motion 


General Theatres Equipment Corp. and 
subsidiary companies, excluding Cinema 
Building Corp., J. M. Wall Machine Co., 
Inc., and Zephyr Shaver Corp., report con- 
solidated net profit, after provision for de- 
preciation and estimated normal Federal in- 
come tax, for the three months ended March 
31 of $145,544. This compares with con- 
solidated net profit of $120,265 for the cor- 
responding period last year. 


(Continued from page 10) 

of a prize fight. Progress was at first 
slow, but, by the late nineties and early 
nineteen hundreds, motion picture 
shows — often referred to as nickelodeons 
— were becoming more common. Pro- 
duction was low, however, and the quan- 
tities of film on hand were necessarily 

These early films were short. A show 
usually consisted of one, or at most two, 
subjects. The show lasted twenty to 
thirty minutes. Twenty to thirty shows 
were put on daily; but the seating 
capacity of the theatres, many of which 
were remodeled stores, usually did not 
exceed one hundred. 

Because of the constantly increasing 
use of motion picture film, which is not 
backed or interleaved with paper, and 
because of some serious fires that ocur- 
red in theatres and exchanges, the East- 
man Kodak Co. became vitally interested 
in the problem of fire prevention. 

In 1906 Kodak began experimenting 
with cellulose acetate, which has the 
same transparent properties as cellulose 
nitrate and in addition is no more in- 
flammable than paper, wood, or many 
other forms of ordinary cellulose. In 
addition to its lower inflammability, 
cellulose acetate will not decompose 
readily when heated; and, except for 
carbon monoxide, it does not give off 
toxic gases when it burns. No more 
carbon monoxide is released from cellu- 
lose acetate when it is burned in a 
limited air supply than is given off by 
equal quantities of ordinary cellulose, 
such as paper or wood. 

• Acetate Film Unsuitable 

In 1909 Eastman had developed cellu- 
lose acetate to a point where the Com- 
pany felt it could be substituted for 
nitrocellulose in motion picture film. To 
give effect to this development, Mr. East- 
man arranged a meeting with the leaders 
of the motion picture producing com- 
panies. Because the advantages of the 
new film were obvious to all, little argu- 
ment was needed to reach an agreement 
whereby only cellulose-acetate film was 
to be supplied by the Company there- 

Experience demonstrated, however, 









Projectionist Restores 
Sound in Four Minutes 
After Filter Bank Shorts 

Time: 11 P.M. 

Place: A theatre in St. Paul, Minn. 

When sound went out at 11 P.M., the projectionist called the Altec 
man. One filter bank had shorted. 

But— because of a special modification made months before by Altec 
—the projectionist knew exactly what to do. 

Accordingly, he first checked "No plate current on the 46 type ampli- 
fier." Immediately he knew what needed to be done. He disconnected first 
one of the emergency cut out loops and then the other, to determine which 
filter condenser bank had failed. Then he left that loop disconnected 
which restored the sound. 

The entire operation, in the projectionist's own words, took exactly 
four minutes before sound was restored. 

The modification, made months before by Altec, which made it pos- 
sible for the projectionist to restore sound so quickly, consisted of chang- 
ing the wiring of the filter banks in the high voltage power circuits of 
the amplifier, so that either bank could be disconnected in a few seconds 
by merely removing a wire from an easily accessible terminal on the front 
of the amplifier. 

These terminals, one for each filter bank, were marked— "Filter Con- 
denser Banks— Cut Out Loops." 

The next day the Altec inspector quickly isolated the particular con- 
denser that had failed in the filter bank, replaced the condenser with one 
from his emergency material kit. 

Because the theatre was operating under an Altec Repair and Replace- 
ment Contract, there was no charge made, either for the material involved 
or for the emergency call. 



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APRIL 1939 


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that acetate film was not as strong me- 
chanically as nitrocellulose film and that 
it became brittle with use. Difficulty 
in the projection of the acetate film 
was experienced partly because of the 
inferior quality of the film but also 
because of the inferior projection equip- 

ment of that day and the rough handling 
to which the film was subjected. 

Although some improvements ensued 
in film, in projection equipment, and in 
handling, the motion picture producers 
asked in 1911 to be released from their 
agreement to use only cellulose-acetate 

film. Thus, in less than two years, the 
Eastman first attempt to substitute slow- 
burning cellulose-acetate film for nitro- 
cellulose film came to an end. This at- 
tempt failed, not because of lack of 
co-operation on the part of the motion 
picture producers, but because of the 
failure of the cellulose-acetate film to- 
perform satisfactorily under the condi- 
tions to which it was subjected. 

The period from 1911 to 1922 was one 
of research, education, and co-operation: 
research in methods of making the pro- 
duction, distribution, and exhibition of 
motion pictures safe to the public and 
the workers involved; education of 
everyone involved in these activities, in- 
cluding not only the industries them- 
selves but also the fire departments, 
transportation companies, and public 
officials, local, state, and national; and. 
finally, complete co-operation which re- 
sulted from these research and educa- 
tional undertakings. 

With the return in 1911 to the pro- 
duction and use of nitrocellulose film 
for the motion picture industry, East- 
man co-operated wholeheartedly with 
the motion picture producers, the na- 
tional and local boards of underwriters, 
the National Fire Protection Association, 
and the various governmental bureaus 
and administrators, in the development 
of devices and methods to control the 
fire hazard in the production, distribu- 
tion, and use, of cellulose-nitrate film 
for motion pictures. 

Although in a period of five years — 
1912 to 1917— the reports of the N. Y. 
City Fire Dept. show that film was the 
cause of only 12/100ths of one per cent 
of the number of fires in N. Y. City, 
and 28/100ths of one per cent of the 
losses by fire, the potential hazard in 
the use of the film was realized. As a 
first official step, ordinances were 
passed, at the instigation of the boards 
of fire underwriters, to make the projec- 
tion of motion pictures in the theatres 
safe for the public. 

• U. S. Government Survey 

Following the Ferguson Building fire 
in Pittsburgh on Sept. 7, 1909, the U. S. 
Geological Survey made a thorough in- 
vestigation to determine the probable 
causes. From this investigation, and 
from laboratory tests, it was concluded 
that the explosion accompanying that 
fire was caused by the ignition of gases 
generated under pressure in a closed, 
unvented vault in which a quantity of 
nitrocellulose film decomposed after be- 
ing ignited by the breaking of an elec- 
tric light bulb. This explosion did not 
occur in the vault, but the gases which 
escaped into an adjoining room formed 
an explosive mixture with the air of the 
room and were ignited by a fire burn- 
ing outside the vault. 

The laboratory tests made at that time 
confirmed these conclusions and proved 
that nitrocellulose film is not explosive; 
and proved, furthermore, that the gases 
generated by film decomposition at at- 
mospheric pressure are of a low inflam- 
mability, but that, if the film decom- 
poses under pressure, the gases gener- 



ated, when properly diluted by air, arc 

The results of these tests were given 
wide circulation, and ordinances were 
enacted, in practically all of the major 
cities, requiring the projection rooms in 
motion picture theatres to be amply 
vented to the open air and to be com- 
pletely isolated from the theatre audi- 
torium. These precautions and other re- 
strictions — plus education as to the vol- 
ume of film and its hazards — are largely 
responsible for the practical absence of 
fires in motion picture theatres. 

Another source of hazard lay in the 
wornout, obsolete, or discarded film. 
With the greatly increased use of mo- 
tion pictures and with longer subjects, 
this obsolete film piled up rapidly in 
the exchanges. In 1918, Eastman in- 
augurated the plan of purchasing this 
discarded film, for recovery of its con- 
stituent materials for non-photographic 
purposes. The film was, and still is, col- 
lected and shipped to Kodak Park, 
Rochester, and to other responsible con- 
verters,, thus removing one of the great- 
est sources of fire hazards in the ex- 
changes. In addition, safe methods 
were devised for handling this scrap, 
and these were made available to others 
who wished to carry on the recovery of 
scrap film as a business, with safety to 
property and life. 

Despite the fact that the number of 
fires and losses attributable to nitrocel- 
lulose film continued small in compari- 
son with other causes, such as gasoline, 
matches, smoking, and carelessness, 
agitation against the use of nitrocellu- 
lose film continued. 

In 1915 the committee on explosives 
and combustibles of the National Fire 
Protection Association, in co-operation 
with the N. Y. City Fire Department and 
the Universal Film Co., conducted a 
test at Fort Lee, N. J. by burning a 
large quantity of discarded motion pic- 
ture film in a vault which, though 
properly vented, was not equipped with 
automatic sprinklers. 

This test was very spectacular. No 
explosion accompanied the fire, but the 
heat was so intense that a giant torch- 
like blast of flame shot horizontally out 
of the vault vent for many feet. Numer- 
ous tests which had been made by East- 
man in its work of protecting its em- 
ployees and its own property from the 
hazards of film fires, had demonstrated, 
previous to the Fort Lee tests, that 
properly arranged sprinklers will con- 
trol film fires. 

Immediately following the Fort Lee 
tests, the Eastman Company, believing 
that the severity of fires under con- 
ditions of the Fort Lee tests could be 
greatly lessened and could be control- 
led, ran a series of tests in 1915 and 
1916 to determine the inflammability of 
film, the protective effectiveness of 
water in varying quantities from 
properly arranged sprinklers, and the 
protective effectiveness of various 
methods of packaging and storing mo- 
tion picture film. 

In the Eastman tests, conditions as 



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to volume and arrangement of film were 
equal to or more severe than the con- 
ditions in the Fort Lee tests. These 
tests, together with earlier tests run by 
the Company, proved conclusively that, 
with properly constructed and vented 
vaults, film fires can be readily extin- 
guished by sprinklers, and, in addition, 
decomposition can be prevented from 
communicating to other films in the 
same storage racks. These tests also 
proved that, in properly vented vaults, 
sprinklers will cool the Hberated gases 
so that explosion, or even ignition, of 
liberated gases is improbable. 

These tests were witnessed by officials 
of the N. Y. City Fire Dept. and also 
by representatives of the underwriters 
and insurance companies. The results 
did much to convince these people that 
film fires in vaults can be controlled by 
automatic sprinklers, with proper vent- 
ing and with proper limitation of quan- 
tity stored; and also that the safe stor- 
age of large quantities of film is possi- 
ble if proper precautions are taken. 

While the Eastman Co. was experi- 
menting with methods of fire prevention 
for nitrocellulose film, the inspection 
department of the Associated Factory 
Mutual Fire Insurance Companies was 
carrying on similar experiments with 
pyroxylin plastics, commonly known as 
Celluloid. A comprehensive report of 
these tests was published in 1916. 
Pyroxylin contains nitrocellulose similar 
to that used in motion picture film. The 
findings in this report were in agree- 
ment with the findings of the U. S. Geo- 
logical Survey in the investigation of 
the Ferguson Building fire in Pitts- 
burgh. This latter report, however, in- 
cluded definite specifications for limita- 
tion of storage-vault capacity and for 
adequate venting and sprinkling. 

In 1919, the N.F.P.A.'s committee on 
explosives recommended a similar code, 
or specification, for the storage of cellu- 
lose-nitrate film. These reports, and 
those of the Eastman experiments in the 
same years, dealt with the fundamentals, 
and have formed the basis, first, for fire 
underwriters' rulings, and, later, for 
laws and ordinances governing the trans- 
portation, storage, and handling of 

all nitrocellulose motion picture film. 
From 1916 to 1919, Eastman prepared 
a series of booklets entitled, "Sugges- 
tions on Fire Prevention." The first 
booklet dealt with automatic sprinklers; 
the second, with housekeeping; the third 
with motion picture film, its character- 
istics and hazards; and the fourth with 
the results of the tests on motion picture 
film fires in vaults. Arrangements were 
made with the motion picture producers 
to make these booklets available to all 
persons in the industry responsible for 
the production, processing, handling, 
and storage, of film. These booklets, 
except one describing the tests, were 
written in plain, non-technical language, 
so that their message could be readily 
understood by the non-technical em- 
ployees in the industry. 

• Field Educational Work 

In addition to this prepared material, 
the Eastman offer to send out experts 
to all exchanges to inspect the ex- 
changes and instruct the managers in 
proper fire-prevention methods was ac- 
cepted by the motion picture producers. 
Six men were specially trained for this 
work and covered the four hundred ex- 
changes in the U. S. and Canada. 
Formal and very complete reports of 
these inspections were forwarded to the 
exchange managers and also to the offi- 
cials at the headquarters of the com- 
panies owning the exchanges. 

Following the first inspections, the 
Eastman Company, collaborating with 
the Fire Underwriters and with various 
government agencies, drew up plans and 
specifications for film exchange build- 
ings. These plans and specifications 
were so prepared that they could be 
readily adapted to local conditions, and 
they were made available to motion 
picture producers and to others who 
wished to build new film exchanges or 
to rehabilitate existing ones. Eastman 
also provided a consulting service for 
the producers in this work. 

Follow-up inspections showed that 
conditions had materially improved, in- 
dicating that, if those vitally interested 
in the problem of fire prevention are 
informed, effective co-operation is pos- 

(giWfflie SAYS- 


Jq~wa4 Aata 1o~i 



ou/t ~ttou{KZ ivatttf'ux toe fZtenectum 
Atrtmi, -vut~4mce ke tchnnu/ * sr\ 

advice a*ut ' gc^ihatneu/ 















sible, This work of inspection and con- 
sultation was carried on by Eastman 
until 1922, when it was turned over to 
the newly organized M.P.P.D.A. The best 
evidence that that organization has suc- 
cessfully carried on the work is to be 
found in the comparative absence of ex- 
change and theatre fires, even with the 
constantly increasing volume of film 
produced and handled. 

Beginning in 1922 and continuing up 
to the present time, we have had a long 
period of consolidation of the progress 
made and of assimilation of the informa- 
tion developed by experience and experi- 
mentation. Although — -as has been 
pointed out — the number of fires and the 
amount of fire loss caused by film, or 
in which film became involved, had been 
small, compared with numbers and 
losses from other causes, there had been 
a number of spectacular fires. 

• Proposed Mtro Ban 

In spite of the fact that investigations 
following these fires showed that, in gen- 
eral, known preventive measures had 
not been properly applied, there were 
demands periodically to outlaw the use 
of nitrocellulose film. In 1919, at 
Ottawa, the resolutions committee of 
N.F.P.A. offered the following resolu- 
tion: "The universal adoption and ex- 
clusive use of slow-burning motion pic- 
ture film with national, provincial, state 
and local legislation to prevent the con- 
tinued manufacture and distribution of 
material having the hazardous properties 
of gun cotton stock now commonly em- 

This was Item 10 in a series of eleven 
items in the resolutions proposed by the 
committee. Item 10 caused more dis- 
cussion than all the other ten items in 
the proposed resolutions, combined. 
There was a decided difference of 
opinion; but, because of the extensive 
laboratory tests and practical full-scale 
tests that had been carried on to deter- 
mine the nature and hazards of cellu- 
lose-nitrate film, and because of the 
demonstrated effectiveness of methods 
of control, the great preponderance of 
opinion favored regulation of use rather 
than imposing the impractical alterna- 
tive in Item 10 on the great and growing 
industry of production and exhibition 
of motion pictures. The resolutions, 
when adopted, formed the platform for 
the year, and were used as the basis 
of insurance-rate rulings and require- 
ments and for legislation to make them 

• Acetate Film Unsuitable 

Experience with cellulose-acetate film 
for commercial motion pictures in the 
years 1909 to 1911 had demonstrated 
that it was entirely unsatisfactory. Prog- 
ress had been made in improving its 
wearing qualities, but in 1919 it still 
was far behind nitrocellulose film in 
this respect. 

Legislation in practically all com- 
munities had been enacted to make the 
exhibition of nitrocellulose film safe for 
the public. The conditions in the ex- 
changes had been improved, and the 

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Eastman Co., at the time of the Ottawa 
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ducers to improve still further the con- 
ditions in the exchanges. Tests by gov- 
ernment agencies and by others had 
proved that nitrocellulose film is not ex- 
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records proved that the number of fires 
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pared with the number attributable to 
any other cause. 

All of these facts, and others, were 

brought out in the discussion of Item 
10 of the 1919 resolutions. As a re- 
sult, the resolutions as finally adopted 
included a revised Item 10, reading as 
follows: "That the use of motion pic- 
ture projection machines without a 
standard booth ventilated to the out- 
side of the building, in churches, 
schools, clubs, hospitals and homes, be 
prohibited unless the film used is of the 
slow-burning type and that state and 
municipal laws and ordinances be 
adopted regulating motion picture ex- 

APRIL 1939 


changes, tending toward the ultimate 
end that motion picture films of the 
nitrocellulose type be replaced when 
practicable by a slow-burning film." 

The great majority of the membership 
of the N.F.P.A. is made up of men rep- 
resenting the insurance companies, of 
fire underwriters, and of public officials. 
Only a small number of members repre- 
sent either the film manufacturers or the 
motion picture producers. When these 
facts are taken into consideration, the 
action taken on this resolution is con- 
vincing evidence of the enlightened 
co-operation which made the control of 
fire hazard in the motion picture indus- 
try possible. 

The M.P.P.D.A. had taken up, shortly 
after it was organized in 1922, the edu- 
cational and inspection work started by 
Eastman in 1919, and had accomplished 
much in the control of use, transporta- 
tion, and handling, of nitrocellulose film. 

From time to time, however, nitrocel- 
lulose film appeared in stores and found 
its way into use in improperly protected 
projectors. In addition, scrap nitrocel- 
lulose film was in some cases trans- 
ported and handled in an improper 

Because of these difficulties, the 
N.F.P.A. public-information committee, 
in its report in 1923, proposed recom- 
mending to the states and provinces of 
the United States and Canada the enact- 
ment of a model law to control the use 
of nitrocellulose film. This model law 
provided for "the control of use of nitro- 
cellulose motion picture film and for the 
licensing of manufacture, use, handling, 
disposition, and transportation of such 

As in the case of the 1919 resolution, 
this proposed law was thoroughly and 
earnestly discussed. No one opposed 
the idea of regulation or the necessity 


These films have been prepared under the supervision of the Projection 
Practice Committee of the Society of Motion Picture Engineers, and are 
designed to be used in theaters, review, rooms, exchanges, laboratories, 
factories, and the like for testing the performance of projectors. 

Only complete reels, as described below, are available (no short sections" 
or single frequencies). The prices given include shipping charges to all 
points within the United States; shipping charges to other countries are 

C ^ — i 

35 -Mm. Visual Film 

Approximately 500 feet long, consisting of special targets with the aid 
of which travel-ghost, marginal and radial lens aberrations, definition, 
picture jump, and film weave may be detected and corrected. 

Price $37.50 each. 

16-Mm. Sound-Film 

Approximately 400 feet long, consisting of recordings of several speak- 
ing voices, piano, and orchestra; buzz-track; fixed frequencies for focus- 
ing sound optical system; fixed frequencies at constant level, for de- 
termining reproducer characteristics, frequency range, flutter, sound- 
track adjustment, 60- or %-cycle modulation, etc. 

The recorded frequency range of the voice and music extends to 6000 
cps.; the constant-amplitude frequencies are in 11 steps from 50 cps. to 
6000 cps. 

Price $25.00 each. 

16-Mm. Visual Film 

An optical reduction of the 35-mm. visual test-film, identical as to 
contents and approximately 400 feet long. 

Price S25.00 each. 

Address i 


Hotel Pennsylvania New York, N. Y. 

for such regulation. A minority, how- 
ever, felt that the Association should 
not pass such a recommendation, but 
should again go on record as supporting 
the early substitution of slow-burning 
film for nitrocellulose film for all pur- 

After much debate which again 
brought out the progress which had been 
made in the control of the fire hazard 
in the use of nitrocellulose film, the 
Association adopted unanimously the 
committee's proposed model law. This 
action and the action at Ottawa in 1919 
are good examples of an association 
membership made up principally of per- 
sons not selfishly interested in a com- 
mercial enterprise taking constructive 
action to safeguard the interests and 
well-being of the public, instead of de- 
structive action, which could not have 
been as fruitful in safeguarding the in- 
terests of all concerned. 

As further evidence of the M.P.P.D.A.'s 
interest in the matter of public wel- 
fare, attention should be directed to its 
reports to the 1924 and 1925 annual 
meetings of the N.F.P.A.. These are 
progress reports giving accounts of 
co-operation and outstanding accom- 
plishment. (Co-operation, I must point 
out again, is the thread that has run 
through the whole fabric.) 

More thorough and more frequent in- 
spections, co-operation with and from 
local fire departments, introduction of 
fire drills, circularization of exchanges 
with educational matter, sponsoring of 
bills for the control of use of nitro- 
cellulose motion picture film, are some 
of the activities of the M.P.P.D.A. Film 
boards of trade were organized in many 
cities. These boards included in their 
membership both the members of the 
M.P.P.D.A. and of the independent 
companies. Thus the organized efforts 
in accident and fire prevention were ex- 
tended to the entire industry. 

This educational and inspection work 
has been carried on by the M.P.P.D.A. 
to the present day. The annual cost, 
although heavy, is justified by the re- 
sults. The increase in volume of film 
handled has been enormous, and the 
number of persons involved in the many 
necessary operations has increased ac- 
cordingly. The price of safety in any 
industry is eternal vigilance. The only 
guarantee that such vigilance will not 
slacken is to be had through a follow- 
up which will develop intelligent, whole- 
hearted co-operation from each and every 
member of the industry. 

Naturally, this story told by the East- 
man Kodak Company, in spite of effort 
to view it dispassionately, must needs be 
colored to some extent by the Company's 
interest in the matter. If its actions were 
said to be motivated by self-interest, 
however, it was at the very least an 
enlightened self-interest, and the same 
is no less true of the motion picture in- 
dustry as a whole. As I said in my 
opening remarks, it is a story of accom- 
plishment of great value to the public, 
made possible by one dominant factor — 



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• • • 

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Visitron cells are available for every type of sound projec- 
tion equipment. Theatre supply dealers can advise the 
correct cell for your equipment. Buy from your supply 
dealer. If you wish to have your old cells tested without 
charge, write to G-M Laboratories, Inc., for instructions for 
shipping. Information furnished promptly. 

"I dropped into the Majestic the other night. 
There's where I'm going after this when I want 
to really enjoy a show. I've never seen better 
theater lighting. I found my seat without stum- 
ping and groping. My eyes didn't get tired and 
I figured that was because there was no sharp 
contrast between the screen and the walls 
around it. It was a color feature and I've never 
seen more natural color on the screen." 

Patrons do comment in this manner on thea- 
ters they visit and their friends respond to their 

impressions. When people desire to see a partic- 
ular feature they go to a theater they know will 
present it properly and in comfortable surround- 
ings. Such presentation means just one. thing — 
high intensity projection. 

Simplified High Intensity projection costs little 
more than obsolete low intensity projection. 
But it does give your patron the impulse to return. 

Ask your Dealer's Salesman for the 
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MAY 1939 




Todays critical audiences' demand for quality projection can best 
be met with Peerless Magnarc High Intensity Lamps. 
In no other lamp is it possible to obtain so much value for first 
cost expenditure and such a great degree of purchase satisfac- 
tion after installation. The proof of this lies in the fact that 
Peerless Magnarc outsell all others two to one. 
High intensity projection has been found an absolute 
necessity by one-third of all theatres in the United 
States — and these theatres have 75 per cent of the 
total seating capacity of the country. 

This modernizing of projection has been brought 
about mainly by Peerless Magnarc's ability to 
produce 200 to 300 per cent more light on the 
screen for the same current cost of low in- 
tensity lamps. Think what this means in 
better picture quality, audience satis- 
faction, competitive advantage. Then 
write for the new folder, "Get A Seat 
On The Bandwagon." 


Sold by National Theatre Supply Co. 



Edited by James J. Finn 

Volume 14/ 

MAY 1939 

Number 5 

Index and Monthlv Chat ...... 


Panic, the Butcher 


The Copper-Sulphide Rectifier. . 


Weber Announces Syncro-Mag- 


netic Soundhead 


Fundamentals of Mathematics. . 


Film Preservative Tests 


George Logan 

Many Important Changes in 
N.F.P.A. Projection Room 

New Erpi Mirrophonic 'Master' 
Theatre Sound System .... 




New Projectors by Brenkert, 

Boston Projectionist Writes His 

Wenzel; Forest Lamp; Brenk- 

2nd Fine Travel Book 


ert-RCA Sales Tieup 


13 Winners in Final Diagram 

News Notes 



Technical Hints 

Process Projection Specifications 


Academy Report 

Miscellaneous Items 

Published Monthly by 



Circulation Manager, Ruth Entracht 

Subscription Representatives 

Australia: McGills, 183 Elizabeth St., Melbourne 
New Zealand: Te Aro Book Depot, Ltd., 64 Courtenay Place Wellington 
England and Dominions: Wm. Dawson & Sons, Ltd., Pilgrim St., London, E. C. 4. 

Yearly Subscription: United 
States and possessions, $2 (two 
years, $3) ; Canada and foreign 
countries, $2.50. Single copies, 
25 cents. Changes of address 
should be submitted two weeks 
in advance of publication date to 
insure receipt of current issue. 
Entered as second-class matter 

February 8, 1932, at the Post 
Office at New York, N. Y. under 
the act of March 3, 1879. 
Contents copyrighted 1939 by 
James J. Finn Publishing Corp. 
International Projectionist 
is not responsible for personal 
opinions appearing in signed 
articles in its columns. 

Monthly Chat 

PERIODICALLY we have commented 
in this space upon the constantly 
growing use of 16 mm. projection equip- 
ment in the professional motion picture 
field. We are all familiar with the many 
applications of such equipment in the 
educational and industrial fields; but the 
widespread use of 16 mm. units for pre- 
senting shows to which admission is 
charged would surprise the professional 
projection craft. 

True, most of these shows are spon- 
sored by itinerant exhibitors who make 
one- or two-night stands in the less 
densely populated territories; but it 
would be no great shock to this corner 
if the producers made available shortly 
16 mm. prints of features not more than 
three months old (from national release 
date) in order to cash in on this rapidly 
expanding field. 

Many such 16 mm. shows charge no 
admission, the program being made up 
of sponsored advertising films. In many 
localities, however, and particularly 
through the South, the traveling exhib- 
itor pitches a tent or hires a vacant store 
or a hall and plays "old" feature sub- 
jects on a 10-15-20-cent admission scale. 
In fact, reports persist that a regular 
circuit of hundreds of such stands is to 
be established throughout the South. 

This situation poses a serious problem 
for the established motion picture theatre 
— and for the projection craft. Reiter- 
ation of our previous suggestion that this 
matter have the close attention of the 
organized projection craft seems to be 
very much in order. We know of no 
more pressing current problem. 

• • • 

Believe it or not, we've received several 
letters lately suggesting that the Projec- 
tion Advisory Council become active 
again. Anybody saying anything? 

• • • 

Technicolor Corp. does some plain and 
fancy weeping in public about the in- 
ability of many theatres to do justice to 
their hued prints. Privately, however, 
this company's efforts to improve color- 
projection can be summed up in one 
word — nothing. 

• • • 

Film breaks, a menace to the safety 
of audience and projectionist and ruinous 
to a good show, are piling up alarmingly, 
reports to circuit headquarters indicate. 
Whatever the cause, discretion dictates 
that pre-show inspection of film is the 
only "out" for Mr. Projectionist, with 
a detailed report being sent to the man- 
ager promptly. 

• • • 

Our British friends are hailing the 
mercury vapor lamp as the "greatest 
advance in projection since sound pic- 
tures". Mebbe so; but this will be news 
even to the overly-enthusiastic American 
sponsors of this light source. 

MAY 1939 


In 1934 a group of engineers looked into the fu- 
ture of the motion picture industry. They were plan- 
ning a copper oxide rectifier for projection service. 
The foremost thought in their minds was that you 
fellows must be freed from the fear of frequent de- 
sign changes if you are to buy the equipment you 

The result of this careful planning was the con- 
servatively-designed G-E Copper Oxide Rectifier for 
Motion Picture Projection Service. 

Its designers gave you the 3-unit transformer for 
greater efficiency. They remembered that you wanted 
a minimum of operating noise and heat, so they pro- 
vided for it. A remote control system was added to 
enable the rectifier to be controlled from the lamp 

pedestal. Control of the rectifier was so simplified 
that the simple opening and closing of the 110-volt 
control circuit was sufficient to start the blower 
motor, close the relays, and automatically connect 
the 3-phase line to the transformer. 

Today that G-E Copper Oxide is the same rectifier. 
The single major change was the division of the unit 
into two parts for your convenience in handling and 

The story will be the same in the future. You can 
buy with confidence now, because changes will be 
few. It was "right" to begin with. That's what counts. 

Write to us now for more information. Section 
A-9455, Appliance and Merchandise Department, 
General Electric Company, Bridgeport, Connecticut. 






MAY 1939 

The Copper— Sulphide Rectifier 

A RECTIFIER may be defined as 
a device for converting alternating 
current into unidirectional current 
I>y mechanical, chemical, or electrical 
means. Probably the most common 
mechanical rectifier is the motor-genera- 
tor set. Another familiar type is the 
rotary converter. All rotating mechani- 
cal rectifiers are equivalent to convert- 
ing the alternator source to a d. c. 

Another mechanical rectifier that has 
wide application in the low-current field 
is the vibrator type, employing a tuned 
reed. This rectifier is used in about 
90 per cent of all automobile radios, 
although in many cases, in this appli- 
cation, it acts as an inverter instead of 
a converter. Another form of mechani- 
cal rectifier is the mercury-jet type, 
wherein a jet of mercury oscillates at 
appropriate frequencies between con- 
tacts performing the commutation. All 
mechanical rectifiers depend upon phy- 
sical connection and the opening of an 
a. c. circuit at the correct times. 

For the sake of simple classification, 
thermionic rectifiers such as vacuum- 
tubes, gas-filled tubes, and mercury 

tj. Soc. Mot. Pict. Eng., XXXII (May 1939). 



Controversial indeed is the topic of power supply for theatre projection arcs. 
The accompanying paper, and particularly the appended discussion, contains 
extremely interesting data anent one such unit, including consideration of con- 
struction, operation, degree of dependability, and life — questions bearing on 
which have long claimed the keen interest of projectionists. 

arcs, fall into the electrical group. 
The vacuum-tube rectifier employing a 
hot filament is a familiar example, as 
it is found in practically every home 
radio set. A less familiar type, but of 
wide commercial usefulness, is the mer- 
cury-arc rectifier. One form consists of 
a hot cathode spote on a mercury pool 
to which the anode current flows. In 
another type, a hot cathode operates 
in mercury vapor. 

• The M-C-S Unit 

A rectifier falling in the electrical 
class and with which the balance of 
this article will deal, is the magnesium- 
copper-sulfide dry disk, or plate, recti- 
fier, first developed about fifteen years 
ago by S. Ruben. It consists of an 
electropositive conductor and an elec- 
tronegative semi-conductor in more in- 

timate contact than physical juxtaposi- 
tion and pressure can give. The elec- 
tropositive element is magnesium; the 
electronegative element is copper-sul- 

The rectifier is electronic in opera- 
tion, the current flowing from the sul- 
fide element to the magnesium element. 
In this, the conducting direction, the 
voltage drop across the junction is ex- 
tremely low, remaining practically con- 
stant regardless of load. In the non- 
conducting, or blocking direction, the 
resistance of the rectifying junction is 
quite high. Electric current flows when 
the magnesium is made negative with 
respect to the polarity of the sulfide 
side; and blocks the flow of electricity 
when made the positive side. 

The magnesium-copper-sulfide recti- 
fier is known as the non-integral type, 

MAY 1939 

because the two components of the 
rectifier have a rectifying film formed 
between them by an electrical process. 
Because of the unique way in which 
the rectifying film is built up, it can 
stand overvoltage which, if it results 
in breakdown of the rectifying film, 
instantaneously heals itself without 
damaging the rectifier. 

Any attempt to explain exactly how 
a contact rectifier operates usually be- 
comes very much involved. It is be- 
yond the scope of this article, there- 
fore, to enter into a highly theoretical 
discussion of the physical principles 
underlying its operation. Suffice it to 
say that a rectifier that depends upon 
electronic action may be likened to a 
valve or gate: it opens the a. c. circuit 
60 times per second when the half- 
cycle is of one sign, and closes the 
circuit when the half-cycle is of the 
opposite sign. Such rectifiers are all 
metallic, and have no moving parts, 
hot cathodes, glass parts, or other 
fragile constructional components. 

The theatre projection arc affords an 
ideal application for the copper-sulfide 
rectifier. These arcs usually operate 
on currents varying from 50 to 65 am- 
peres at 35 volts. These values are 
particularly well suited to the copper- 
sulfide rectifier, which is fundamentally 
a high-current, low-voltage type. 

In order to evaluate the magnesium- 
copper-sulfide rectifier in terms of use- 
ful power-supply devices for projection, 
it will be necessary at this point to 
describe several fundamental facts by 
which the performance of the sulfide 
rectifier is measured. 

• Performance Measurements 

The first fact to establish is how 
much a. c. voltage will one rectifying 
junction block; in other words, how 
much a. c. voltage can be applied 
across the components of a junction 
without breaking down the insulating 
film between them. The magnesium- 
copper-sulfide rectifier will stand 3 to 
3.75 volts rms. on load per junction. 
These are working voltages. Blocking 
peak voltages would be 1.4 times these 
values. When these values are exceeded 
by 15 or 20 per cent there is the possi- 
bility of breakdown, resulting in rapid 
deterioration of the junction if the con- 
dition causing the breakdown persists. 
However, as previously stated, occa- 
sional overvoltage due to line surges, 
etc., causing momentary breakdown in 
the rectifying film, will not affect the 
normal operation of the rectifier or its 

Closely related to the permissible 
volts per junction is the ratio of d. c. 
output voltage to a. c. input voltage. 
For three-phase, full-wave bridge opera- 
tion it has been found that the voltage 
ratio of the magnesium-copper-sulfide 

rectifier is about 85 per cent. In the 
case of the rectifier for projection, this 
means that 44 volts a. c. are impressed 
across a sufficient number of junctions 
in series to produce 35-36 volts d. c. 
at the arc. Another important factor 
is the current ratio; that is the ratio 
of the d. c. output to the a. c. input. 
The rectifier has approximately a 120 
per cent current ratio for three-phase, 
full-wave circuit system 

Having reviewed rectifiers in general 
and discussed the mechanism of the 
contact rectifier in particular, we can 
now consider details of design for a 
rectifier power supply for the projec- 
tion arc. The essential features are: 

(1) Most suitable type of a. c. cir- 
cuit system. 

(2) Current-handling capacity of the 
sulfide rectifier as a function of life 
and operating temperature. 

(3) Cooling or ventilating methods. 

As most projection arc rectifier ap- 
plications call for d. c. voltages vary- 
ing from 35 to 50 volts, it is necessary 
to employ a transformer to step-down 
the 110- or 220-volts a. c. source to a 
suitable value to be used in the arc 

Two basic circuits are employed with 
all contact rectifiers: the half- wave and 
full-wave bridge, single-phase or poly- 
phase. The full-wave bridge requires 
twice as many rectifier elements as the 
half-wave for the same voltage input. 

Various circuit systems 
used with sulphide rec- 

is the same as the forward voltage) 
and requires fewer junctions than some 
of the other polyphase systems. Be- 
cause this is very desirable from an 
application viewpoint, this circuit is 
considered the best, giving, as well, a 
ripple six times the input frequency of 
60 cycles. It may be mentioned that 
where filtering out the ripple is neces- 
sary, the higher its frequency the easier 
it is to filter. 

• Operating Temperatures 

All contact rectifiers are resistance 
devices, therefore, they generate heat 
when rectifying. The normal life ex- 
pectancy of such a rectifier is based 
mainly on its operating temperature. 
The lower the operating temperature, 
the longer the life, when other operat- 
ing conditions are normal. Heat gen- 
erated at the junction must, therefore, 
be removed faster than by simple con- 
vection cooling if the rectifiers are to 
handle large currents such as those 
associated with the carbon arc. 

The magnesium-copper-sulfide junc- 
tion, designed for carbon arc use, hav- 
ing 1.7 sq. in. of rectifying area with 
associated radiator plate of 12J4 sq. in. 
of area, will handle 38 d. c. amperes 
per sq. in. safely and continuously. 
These current-densities are based on 
three-phase, full-wave operation. 

One of the outstanding features of 
the copper-sulphide rectifier is the ability 
to withstand unusually high operating 







HALFWAVE: 60 cycle ripple. 



forward: iao cycle ripple. 








Fig. 1 shows various circuit systems. temperatures. Fig. 4 shows a life-test 
The three-phase, full-wave bridge curve on a copper-sulphide rectifier pur- 
connection with the windings of the posely operated at temperatures con- 
source delta-connected, has the lowest siderably in excess of those encoun- 
blocking peak voltage per element (it tered in the projection arc type of 






A New Amazing Way 

9 Will not thicken, spoil or 

# Retains its full strength to 
the last drop — even when left 
uncovered. Requires no thin- 
ning agent. 

Firmly binds all film — 
nitrate, acetate, color stock. 

# Goes twice as far as 

T TSERS of film cement, and particu- 
larly projectionists, will welcome 
Film- Weld — because it is not a cement! 
Developed in the chemical laboratory 
of a mid-Western university, Film- 

There is a convenient size for 
every user 

1 oz 25c 

V% Pt 75c 

1 Pt $1.25 

to Splice Film 

Weld is as clear as water and just 
as thin. And it never hardens . . . 
nor requires any thinner. 

Film-Weld is compounded to meet 
the exacting demands of modern pro- 
jection — higher film speed and intense 
heat of the new arcs, which impose 
severe strain on the film. Film 
cement was never designed to meet 
these conditions. 

Film- Weld is used the same way as 
old-fashioned cement — but it binds the 
film instantaneously in a splice that 
is ready for immediate use. The splice 
is several thousandths of an inch less 
thick than that made with cement, yet 
it is several times more binding. 


Try a dab of regular cement on 
paper, cloth, rubber, leather, or even 
on your fingers — it sticks there all 
together, like glue. Now try Film- 
Weld the same way. It doesn't even 

make your fingers sticky, 
it works wonders. 

But on film 

Here, at last, is a compound that is 
equally efficient on ALL film — nitrate, 
acetate, and all color prints. Forget 
the cork . . . leave it exposed con- 
tinually ... it will never thicken and 
will maintain its consistency and 
efficiency down to the last drop ! No 
thinner is ever required. 

Developed for the exacting needs of 
the film laboratories and exchanges, 
Film- Weld is now available for 
theatre use. Projectionists will wel- 
come the y 2 pt. bottles especially de- 
signed for their convenience. Film- 
Weld is now being used by the largest 
theatre circuits in the country. 


Buy a bottle of Film-Weld and 
make your splices for a week. Then, 
if you still prefer the old-fashioned 
cement, return the unused portion of 
Film- Weld to your dealer and receive 
your money back. 

Film-Weld is distributed throughout the world exclusively by 


1241 South Wabash Ave. 

Chicago, Illinois 

MAY 1939 


EASTMAN'S three new motion picture neg- 
ative films have quickly established them- 
selves as the favorites of the industry. Plus- 
X for general studio work . . . Stiper-XX for 
all difficult exposures . . . fine-grained Back- 
ground-X for backgrounds and all-round ex- 
terior work. Each makes its special con- 
tribution, and all have that typical reliabil- 
ity closely identified with Eastman films. 
Eastman Kodak Company, Rochester, N. Y. 
(J. E. Brulatour, Inc., Distributors, Fort Lee, 
Chicago, Hollywood.) 

EASTMAN Plus-X ... 

Super-XX . . . Background-X 


rectifier. Remembering that 100°C is 
the temperature of boiling water, it is 
readily understood that a rectifier that 
can withstand such a temperature con- 
tinuously is truly remarkable. Any 
other type of contact rectifier would 
absolutely fail at such a temperature 
or at even much lower temperatures. 

For low current-densities per recti- 
fying junction, where the operating tem- 
perature will never exceed 130° C, the 
simplest method of cooling is convec- 
tion cooling. Where the rectifier is 
required to handle large currents, as in 
the projection arc application, it is 
necessary to employ forced draft or 
so-called fan cooling. 

Where the rectifiers are operating at 
comparatively low current-densities, as 
in the case of the rectifier for the 
theatre carbon arc, a simple adaptation 
of some well-known cooling principles 
may be employed. Such an adaptation 
has been worked out excellently in the 
rectifier shown in Fig. 3. The trans- 
former is placed at the bottom of a 
steel cabinet. The two banks of recti- 
fiers (in the case of a twin arc power- 
supply) are supported in trays imme- 
diately above the transformer. The 
space around the trays is baffled to con- 
centrate the air-flow through the cool- 
ing fins of the rectifiers. 

• Degree of Dependability 

A propeller-type fan blade of suffi- 
cient air capacity to maintain the 
operating temperature of the rectifiers 
considerably below their maximum safe 
operating temperature is driven by a 
motor mounted at the top of the cabi- 
net. This simple cooling arrangement 
draws air in from the bottom, over and 
around the transformer, then through the 
rectifier cooling-fins, with discharge at 
the top, providing efficient cooling in a 
compact assembly. 

for the theatre is dependability regard- 
less of the type of source. 

Rotating equipment requires periodic 
servicing and maintenance. The 
magnesium-copper-sulfide rectifier, if 
properly ventilated and not subjected 
to abnormal operating conditions, per- 
forms satisfactorily over a long period 
of time without any attention whatso- 
ever. Because of the large margin of 
reserve capacity in this rectifier de- 
signed for theatre use, fan failure will 
not darken a theatre. Instances have 
been reported from the field where the 
fan associated with a copper-sulfide 
rectifier for theatre use had failed and 
could not be replaced immediately, but 
the rectifier carried on for days until 
a new fan was installed. Such operat- 
ing conditions are not to be encour- 
aged, but they go to show that in the 
copper-sulphide theatre rectifier there is 
a power-supply available requiring 
practically no maintenance and one 
that will stand considerable punishment 
without failure. 

Naturally, the theatre owner is inter- 
ested in the all-around performances of 
this power-supply and how long it will 
last. An extensive life-test has been 
run on the copper-sulfide rectifier em- 


Commercial form of sulphide rectifier 

with forced ventilation, for projection 

arc power supply 

rectifier power-supplies such as for 
electroplating, delivering 3,000 d. c. 
amperes and upward, indicate that 
these improvements now being incorpor- 
ated also in the projection arc recti- 


Life-test of copper-sul- 
phide rectifier designed for 
projection arc supply 




) Lt 


) F 





) e 





















EN r 























r Nl 










i 1 




> C 



























ployed in projection arc power-supplies. 
Fig. 4 shows the results of a test run 
on the machine shown in Fig. 3 ex- 
tended to the equivalent of 10,000 hours 


Fan Blade 


Arrangement for ventilat- 
ing rectifier for large 
power output 

Tap Changing 

Any discussion of power-supply for 
projection arcs immediately raises the 
question of the relative merits of rotat- 
ing equipment vs. rectifiers. Probably 
the most essential feature of such units 

of normal theatre operation. 

Improvement in the technic of proc- 
essing the copper-sulfide rectifier and 
the experience gained during the past 
two years in building heavy-current 

fier will give the theatre a dependable 
source of power with an exceedingly 
long life. 


Mr. Gessin: What is the average life 
of the copper-sulfide rectifier? 

Mr. Kotterman: That depends upon a 
number of conditions: Operating tempera- 
ture for one thing, variation in load, and 
the type of adaptation. For theatre use, 
with the improved type of rectifier we are 
now building, we anticipate a useful life 
of five years 

Mr. Crabtree: What is the effect of 
high humidity? 

Mr. Kotterman: None. The radiating 
fins and the rectifying elements are 
clamped together on a very heavy bolt, 
with spring washers at either end, to main- 
tain constant pressure regardless of con- 
traction and expansion during operation. 
The assembly is vacuum-impregnated with 
special varnish which prevents moisture 
from getting into the rectifier elements. 

Mr. Crabtree: Magnesium is, of course, 
readily oxidized. 

Mr. Kotterman: That is one reason 

(Continued on page 28) 

MAY 1939 


Is This Happening To You? 

lerica's Movie Fans Demand Good Sow 

y![lHl]y![l]kHi T ifi!HWlll[Nfniii 

enables you to give them the best! 

AlOOf £ 

Fine new equipment has "partner" for Rotary 
Stabilizer — amazing new Shock-Proof Drive! 

So much emphasis has been placed on sound by 
Hollywood movie men that far-sighted exhibitors can 
no longer overlook the necessity of modern sound 

Movie makers are concentrating on sound because 
the public demands good sound. And the public nat- 
urally patronizes the theatres that provide it. 

Your theatre can offer movie-goers the world's finest 
sound — if you equip it with the new RCA Photophone 
Magic Voice of the Screen. You can do this at a price 
within your means. And your increased audiences will 
soon put that price — and more — back in your box office. 

In more than 5000 theatres the Magic Voice of the 
Screen is proving a smart investment, hailed by ex- 
hibitors as a real money-maker. And now RCA Pho- 
tophone offers you a new Magic Voice — equipment 
even better than its popular predecessor — a Magic 
Voice which offers you more important features than 
any other sound equipment in the world! 


Better sound means better box office — and RCA tubes mean better sound. 
RCA Photophone's service organization has a low cost theatre service plan 
in which you'll be interested. 

' el sand- 

OF fv £/?y 


Only the New Magic Voice of the 
Screen Offers all These Features! 

This splendid new equipment gives you full assurance of con- 
stant film speed by adding the amazing new Shock-Proof Drive 
to the famous Rotary Stabilizer! Besides this great feature, the 
new Magic Voice brings you new styling, new protection, new 
convenience, new added reserve power and many other outstand- 
ing proofs that it's the best value you've ever seen! Ask your 
RCA Photophone representative for complete information. 


Fundamentals of Mathematics 



This is the first section of a series of five articles on mathematics. 
The individual sections deal with: 

Section I — Symbols, Definitions, and Square Root. Section II — 
Positive and Negative Numbers, Addition, Subtraction, Multiplication, 
and Division of Monimials. 

Section III — Multiplication, Division, and Factoring of Poly- 
nomials, Ratio and Proportion. Section IV — Simultaneous Equations. 
Section V — Logarithms. 

It will be a help if the reader digest each article as it appears, 
for the ideas presented in subsequent sections hinge upon an under- 
standing of topics discussed in earlier sections. Further, it is desir- 
able that the issues of this series be cached away after reading, as 
back-reference may feet useful before the series is completed. 

The various examples given throughout the series will be best 
u-nderstood if the reader will work them out on paper, duplicating, 
step-by-step, the solutions given in the text. 

IT! /TATHEMATICS is like a favorite 
Wfl tool one keeps in a kit. There 
■*■ may not be a need for it each 

hour of the day, yet when a need does 
arise, that particular tool is indispensible. 
This analogy for math well applies to 
vocations which are basically technical 
in character. All of the phases of mech- 
anical and electrical engineering — de- 
sign, manufacture, operation, and main- 
tenance — recurrently meet up with prob- 
lems which are solved by the creation 
and solution of equations. Mathematics 
is simply logic in one of its purest forms. 
Modern motion picture equipment is 
a nice blending of mechanical and elec- 

■ trical principles; and a technician en- 
trusted with the operation and mainten- 
ance of such equipment is certainly a 
more valuable man if he has a practical 
knowledge of the basic principles in- 
volved. Those physical principles are 
almost invariably expressible in math- 
ematical form. So, to achieve a firm 
grasp on theoretical mechanics and elec- 
tricity, it is imperative that one start 
first with groundwork in math. 

It is the writer's experience — and the 
experience of other engineers with whom 
he has discussed the subject — that by far 
the largest proportion of problems may 
be solved by simple algebraic methods. 
Those problems requiring more involved 
methods are comparatively rare. As a 
result this series will be concerned pri- 
marily with practical algebra. Too, a 
familiarity with algebra is indispensible 
if the studious-minded technician wishes 
to delve further into calculation methods ; 
so there we have another good reason 
for our theme. 

In arithmetic, combinations of the 
numerals 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, are 
used to express quantities. Algebra uses 
these numerals too, but introduces also 
the use of alphabetical letters a, b, c, d, 
e, f, . . . through z to denote quantities. 
There should be no element of mystery 
in such alphabetical symbols, because 
they stand for numbers, and before a 
numerical answer to an algebraic expres- 
sion can be found the numerical equiva- 
lents of the symbols must be substituted 
in the expression. 

The use of alphabetical symbols in de- 
riving and simplifying equations is ad- 
vantageous because it keeps the equation 
in a general form. Once an equation is 
in a simplified general form it may be 
used to solve numerous specific examples 
to which the equation applies. A very 
good example of this is our familiar 
Ohm's law for direct current: 

You see, this is a perfectly general 
equation, and it does not insist that any 
one of its terms have some particular 
value before the equation can be applied. 
On the contrary, the current, or voltage, 
or resistance may be any value; just as 
long as any two of these quantities are 
known, Ohm's law will enable us to 
solve for the third and unknown quantity. 

Various symbols are used in algebra 
to indicate operations to be performed; 
other symbols to abbreviate words. Thus 
the dash line between E and R above 
indicates division of E by R, and the 
symbol = is a brief way of saying 

"equals". Below are the symbols most 
frequently encountered. 
Symbol Definition 

+ "plus," or "positive" 

— "minus," or "negative" 

X "times," or "multiplied by" 

= "equals" 

-~ "divided by" 

^ "does not equal" 

> "is larger than" 

<C "is smaller than" 

.'. "therefore" 

( ) "parenthesis" 

[] "bracket" 

{ } "brace" 

. . . "and so on", or "and so forth" 
In division, the number to be divided is 
called the dividend. The number doing 
the dividing is called the divisor. Thus 
in a -l-b, a is the dividend, b is the divisor. 
Division may be indicated in any one 
of the following ways: 



And a multiplied by b may be written: 
aXb a.b ab 

When you find a parenthesis, bracket, 
or brace fencing in an expression, per- 
form the indicated operations on that 
expression first. 


(4a— 2a) X3=2aX3=6a 

In other words: : 


.'4a— 2a) X3=^4a— 2a X 3 

When multiplication is performed the 
result is the product. When division is 
performed the result is the quotient. 
When addition is performed the result is 
the sum. When subtraction is performed 
the result is the difference. 

If several numbers are multiplied to- 
gether to form a product (and by num- 
bers is meant either arithmetical num- 
bers or alphabetical symbols which stand 
for arithmetical numbers), each com- 
ponent number, and the product of com- 
ponent numbers are known as factors. 
This is similar to the idea of factors in 
simple arithmetic. The number 8, for 
example, is 4X2, and 8 has as factors the 
numbers 4 and 2. 

Consider the term llz. This is a prod- 
uct formed by multiplying together an 
arithmetical number, 11, and an alpha- 
betical symbol for a number z. This 
product therefore has as factors, 11 and 
z. When one of the factors is an arith- 
metical number, as in this case, that 
factor is known as the coefficient of the 
alphabetical symbols in the term. Thus 
11 is the coefficient of z. Similarly, in a 

MAY 1939 


term 4/c, 4 and k are the factors, and 4 
is the coefficient of k. 

When the coefficient is simply 1, usu- 
ally it is not written, but its existence is 
understood. Thus ly is usually written y. 
If a number is multiplied a certain 
number of times by itself, the product 
obtained is called a power of the num- 
ber. The operation of obtaining a power 
of a number is indicated by writing a 
small exponent above and to the right of 
the number like this: y*. 

This is read y to the fourth, or the 
fourth power of y. The number y is 
known as the base, 4 as the exponent or 
index. Writing y 4 is simply a brief way 
of saying: 

As has been stated, if an algebraic sym- 
bol is written without a coefficient, the 
coefficient 1 is understood to exist. That 
is why in interpreting the expression y* 
in detail we write: 

This leads up to the interpretation of a 
number iaised to the zero power, such as: 
b°, or, identically, lb 
Here our exponent tells us that the 
unity coefficient, 1, is not multiplied by 
b any number of times, so that simply 
unity is the result. Hence, any number 
raised to the zero power becomes simply 

b 2 =lXbXb 
b 3 = lXbXbXb 
Finding the root of a number is a 
procedure inverse to that of finding the 
power of a number. A root is one of 
the equal factors of a number. The 
operation of finding the root of a number 
is indicated by the placement of a root 
sign over the number, as 

2 \/64 
which is read the square root of sixty- 
four. The small number nested in the 
root sign is called the index of the root. 
It indicates the number of equal factors 
taken. For example: 

V64=8, for 8X8=64; 
two equal factors taken 
V64=4, for 4X4X4=64; 
three equal factors taken 
An index 2 means the square root, an 
index 3 means the cube root, an index 
4 means the fourth root, an index 5 
means the fifth root, and so on. 

When the square root of a number is 
to be found the index is usually omitted, 
and the number is simply written under 
the root sign. Incidentally, the root sign 
is also known as the radical. Thus the 
square root of 64 would normally be 
written : \A>4. 

While we are reviewing it would be 
advantageous to refresh our minds on 
the method of obtaining the square root 

of an arithmetical number. This will 
give us an opportunity, also, to talk 
in algebraic language, and further show 
the usage of some of the symbols we have 
defined. For oui problem, find 

The first step is to segregate the num- 
ber into groups of pairs, starting at the 
decimal point and working both ways. 
If the decimal portion of the number 
contains an odd number of digits, (a 
digit is any one of the ten figures, 1, 2, 
3, 4, . . .), add a cipher at the right 
end to form a pair. Thus we get: 
7 96. 41 70 

The successive digits which we shall 
find to form the square root of 796.417 
we shall call d lt d 2 , d s , ... In other 
words, d 1 will be the first digit in the 
root, d 2 the second digit in the root, and 
so on. The little subscripts 1, 2, 3 . . . 
written adjacent to the symbol d are 
merely for identification. Subscripts are 
often used for this purpose; they do not 
represent operations. 

Appended hereto is a step-by-step so- 
lution of this problem. After one has 
gone through a few steps one becomes 
aware that the method of the steps is 

7 96.41 70 | 2 

22 = 4 

To find first digit in root, d 1 

The first group is simply 7. Estimate d x 

so that 6 7 ! 2 will not exceed 7. Write d t 

in the root space, write d x 2 under 7, as 


7 96.41 70 | 2 

2 2 = 4 

2X20 = 40 | 3 96 

Subtract 4 from 7, and bring down the 
next group. Multiply the number in the 
root by 20, and place the product to the 
left, as shown. 

7 96.41 70 | 28 

22 = 4 

2X20 = 40 j 3 96 
(40+8)8 = 3 84 

To find second digit in the root, d 2 
Estimate 396/40, to give a trial value 
of d 2 . Hence try d 2 = 8. Place 8 in the 
root." Multiply (40+8) by 8, and place 
the product under 396. If this product 
had been >396, we had estimated d 2 too 

7 96.41 70 | 28 

2 2 = 4 

Subtract 384 from 396, and bring down 
the next group. Multiply the number 
in the root formed by the sequence d a d 2 
by 20, and place the product to the left 
as shown. 

Since we have used up all the digits 
to the left of the decimal point in the 
number, we place a decimal point beside 
8 in the root. 

7 96.41 70 
22 = 4 


2X20 = 40 I 3 96 
(40+8)8 = 3 84 
28X20 = 560 | 12 41 
(560+2)2 = 11 24 

To find third digit in the root, d 3 

Estimate 1241/560, to give a trial value 
of d 3 . Hence try d 3 =2. Place 2 in the 
root. Multiply (560+2) by 2, and place 
the product under 1241. If this product 
had been greater than 1241, we had 
estimated d 3 too large. 

7 96.41 70 | 28.2 
22 = 4 

2X20 = 40 | 3 96 
(40+8)8 = 3 84 
28X20 = 560 1 12 41 
(560+2)2 = 11 24 
282X20 = 5640 [ il 17 70 

Subtract 1124 from 1241, and bring 
down the next group. Multiply the num- 
ber in the root formed by the sequence of 
digits d t d 2 d z by 20, and place the prod- 
uct to the left as shown. 


I 3 96 

3 84 

1 12 




1 1 






2X20 = 40 I 3 96 

(40+8)8 = 3 84 

28X20 = 560 1 12 41 

7 96.41 70 

22 = 4 

2X20 = 40 

(40+8)8 = 

28X20 = 560 

(560+2)2 = 

282X20 = 5640 

(5640+2)2 = 

I 4 86 

To find fourth digit in the root, d t 

Estimate 11770/5640 to give a trial value 
of d 4 . Hence try J 4 =2. Place 2 in the 
root. Multiply (5640 + 2) by 2, and 
place the product under 11770. If this 
product had been >11770, we had esti- 
mated d 4 too large. 

Hence \/796.417= 28.22 very closely. 
The root is not an exact root because the 
last subtraction left a remainder. Here, 
for example, is an exact root: Find 



92 = 81 
9X20 = 180 | 3 64 
(180 + 2)2 = 3 64 

9 2 

| 00 
It is possible to obtain \/796.417 more 
closely than 28.22 represents by finding 
the root to a greater number of decimal 
places. This is done by adding zeros to 
the right-hand end of the number — like 
this, 796.4170000000— and continuing the 
procedure for extracting the root until 
all the zeros are used up. Each pair of 
zeros appended to the number will en- 
able us to find one more digit in the root, 
and the more digits found for the root, 
the more accurate the root will be. Just 
to show how this goes let's find two more 
digits in the square root of 796.417. 

7 96.4170 00 00128.2208 

22 = 


2X20 = 40 13 96 

(40+8)8 = 

3 84 

28X20 = 560 

! 12 41 

(560+2)2 = 


282 X 20 = 5640 1 

117 70 

(5640+2)2 = 

1 12 84 

2822X20 = 56440 

4 86 00 

(56440+0)0 = 

00 00 

28220 X 20 = 564400 1 

4 86 00 00 

(564400+8)8 = 

4 51 52 64 

Thus 28.2208 is a somewhat more ac- 
curate value for \A96.417 than is 28.22. 

It is easy to check the correctness of 
a root. For if one quantity equals an- 
other quantity, the square of the first 
quantity is equal to the square of the 
second quantity. In algebraic language: 

if b = Va~ 

then 6 2 = (Va~) 2 
= a 

(To square a number under a radical, 
simply remove the radical.) 

.". if 9.2 = a/84.64 exactly 
then (9.2)2 _ 84.64 exactly 

.-. if 28.2208 = a/796.417 closely 
then (28. 2208) 2 = 796.417 closely 

To make a check of this nature simply 
square the roots and note if the square 
equals or closely approximates the orig- 
inal number 












Many Important Changes in N. F. P. A. 
Projection Room Regulations 

IMPORTANT changes in the Regula- 
tions for Nitrocellulose Motion Pic- 
ture Film, particularly as applying to 
projection room practice, were adopted 
by the National Fire Protection Associa- 
tion at its annual meeting in Chicago, 
May 8 to 12. The changes were recom- 
mended by the Association's Committee 
on Hazardous Chemicals and Explosives, 
which group worked in close collabora- 
tion with the Projection Practice Com- 
mittee of the S.M.P.E. 

These changes are enumerated below, 
the new wording being indicated by ital- 

191. Enclosures for Motion Picture Pro- 
jectors. For new construction, a size not 
less than 8 feet wide, 10 feet deep and 8 
feet high is recommended for one projection 
machine, and not less than 14 feet wide, 10 
feet deep and 8 feet high for two machines. 

(b) The walls and ceiling of the enclos- 
ure shall be built of brick, tile, or plaster 
blocks, plastered on both sides, or of con- 
crete, or of a rigid metal frame, properly 
braced, and sheathed and roofed with sheet 
iron of not less than No. 20 U.S. gauge 
metal, or with J^-inch hard asbestos board, 
securely riveted or bolted to the frame, or 2 
inches of solid metal lath and cement or 
gypsum plaster. All joints shall be suffi- 

ciently light to prevent the discharge of 
smoke. Non-combustible acoustical material 
may be used on ceiling and wallls, on top of 
the plaster. 

For new construction, it is recommended 
that the walls of the enclosure be constructed 
in accordance with the requirements of sub- 
section 112, paragraphs '1), (2), or (3} T 
for partitions, with floor and ceiling of 
equivalent fire resistance. Modern heavy 
equipment may require special attention to 
floor strength and support. In some cases 
it may be necessary to support the projec- 
tion room independently of the structure. 

Projection Room Doors 

(c) The entrance door into the enclosure 
shall be at least 2 feet by 5 feet, of con- 
struction equivalent to the sheathing per- 
mitted above for rigid frame construction, 
and shall be self closing, swinging out, and 
shall be kept closed at all times when not 
used for egress or ingress. 

For new construction it is recommended 
that at least two doors be provided, each 
not less than 30 inches wide and 6 feet high. 
Doors should be approved fire doors of a 
type suitable for use in corridor and room 
partitions (Class C openings as defined in 
the Regulations on Protection of Openings 
in Walls and Partitions). Exists should 
be in accordance with requirements of 
authorities having jurisdiction, particularly 

(Continued on page 27) 

Boston Projectionist Writes His 2nd Fine Travel Book 

THIS Arthur Foley of Boston projec- 
tionists' Local 182 has something, and 
that something is the ability to turn out 
a travel book which for style, insight, 
humor and inclusiveness puts to shame 
some of those who labor under the handi- 
cap of "professional writer". Every so 
often (or, to be specific, every year) Mr. 
Foley is victimized by a combination of 
claustraphobia (undoubtedly the result 
of a year's work as chief projectionist 
of the RKO Theatre in Boston) and a 
nostalgia for far-away places. And he 
does something about it — he just ups and 

Two years ago his book "Breezy Ad- 
venture," a racy and invigorating record 
of his travels in Europe and in the 
American maritime provinces, provided 
this writer with one of the most exhilir- 
ating travel volumes he ever read. Now 
Mr. Foley has done it again under the 
title of "Italian Ports of Call,"* which 
very aptly is subtitled "Mirth on the 
Mediterranean". It's a pip, even better 
than his previous effort. 

Mr. Foley's latest book is a curious yet 
highly engaging mixture of sentiment, 
humor and practicality. From Boston to 
Gibraltar to Algiers to Naples to Malta, 
with many ports of call sandwiched in 
between, not a thing escapes the shrewd 
observance of the author. Life aboard 

Foley. 213 pages. Bruce Humphries, Inc., 306 
Stuart St., Boston. $2. 

ship, ashore at the various ports of call, 
the varied peoples, customs and note- 
worthy aspects of the many countries 
visited — all these are detailed in such a 
personalized manner as to make the 
reader want to pack his things and yell 
"Let's go!" 

No counting of cobblestones or church 
spires, no straining after historical data 
for Mr. Foley. Not him. He goes 
where we upon our return from a trip 
wished we had gone. Avoiding the well- 
worn "tourist" paths that are so sharply 
etched out in every port in the world, 
Mr. Foley goes off on his own, pokes into 
this, that and the other corner, and 
comes up with the real low-down on the 
locality — he vitalizes the place and 
makes it come to life, so unerring is his 
vision and so sensitive his perceptions. 
And there is beauty in this volume, too 
■ — lots of it. Describing one port of call, 
Mr. Foley disdains to dish up the usual 
romanticism about the "glories of this 
ancient and hallowed city"; instead he 
relates his feelings as he and a charming 
young lady sail out of a moonlit-drenched 
harbor, the while they munch sandwiches 
and have a spot or two. 

Mr. Foley brings to these 213 pages a 
freshness and directness of vision that is 
the basic essential of good narration. 
His senses are alive, his perceptions 
clear, and his conclusions objective in 
the extreme. He's done a swell job, one 
that we enjoyed tremendously. Bravo! 
Arthur.— J.J.F. 

MAY 1939 


13 Winners in Final Diagram Contest 

THIRTEEN winners were registered 
in the seventh diagram offered in 
I. P. last month. The circuit, that of a 
volume control amplifier, presented no 
unusual features, yet there were a sur- 
prising number of errors made by com- 
petent craftsmen who had previously 
worked out much more difficult dia- 
grams. The errors in the diagram (Fig. 
1) are as follows: 

1. Dot added at the first crossing 
below R-l. 

2. Dot added to the right lead to 
VT-1 filament. 

3. Jumper added to the top of R-10 
line running upward from C-7. 

4. Jumper leading from No. 1 ex- 
citer lamp terminal No. 2 removed from 
"Common" and connected instead to 

5. Jumper added, V.C.A. terminal A 
to V.C.A. No. 1 terminal C. 

Those who doped out these circuit 
errors were: Henry E. Jeffery, Cortland, 
N. Y.; E. J. Doolittle, Baltimore, Md.; 
F. J. Pfeiff, Hamden, Conn.; J. J. Ed- 
gerly, Fall River, Mass. ; Louis A. Briggs, 
Rochester, N. Y.; C. E. Mervine, Potts- 


cueecr to „ 
couo. o-\\ 

ville, Penna. ; J. J. Carroll, Newburgh, 
N. Y.; George J. Beltz, McMechen, W. 
Va.; M. D. Faige, Springfield, Mass.; 
George Graff man, Philadelphia, Penna.; 
Jack LeRoy, Groton, N. Y.; M. Rush- 
worth, Baltimore, Md.; and Anthony 
Discavage, Pottsville, Penna. 

• Contest Discontinued 

I. P. has decided to discontinue the 
Subscription Contest Diagram for the 
summer months, which decision was 
prompted by several factors. First, al- 
though there is ample evidence at hand 
to indicate that many readers work out 
the diagram without submitting their 
answers, a checkup discloses that prac- 
tically the same group contribute replies 
each month. This in turn means that 
among the winners there are not a few 
who must already be surfeited with 
complimentary subscriptions. 

Still another reason is the difficulty ex- 
perienced in obtaining diagrams which, 
while applicable to the theatre sound 
picture field, are of such nature as to 
preclude the possibility of an original 
unaltered copy being available to some 
contestants and not to others, thus grant- 


(85 V) 


g/ z cure 

♦WW— o 

«„ CHdUGE 






Power Pack 


CHtniGEOvee *z. 





(vcn. *z) 

ing an unfair advantage to the very few. 

Despite the most careful efforts on the 
part of I. P. to hide the identity of the 
various circuits presented, each month 
saw the receipt of not a few answers in 
which the diagram was readily identi- 
fied. This could mean only that the 
contestant was familiar with the circuit, 
either through actual work thereon or by 
means of circulars distributed, and thus 
enjoyed an unfair competitive edge. 

Undoubtedly there are many contest- 
ants who regard the Contest as admirable 
trouble-shooting practice and would de- 
sire that it be continued even if the free- 
subscription prize angle be eliminated. 
I. P. welcomes expressions of opinion on 
this point from such men, and if there be 
a sufficient number who vote for continu- 
ance of the Contest without the prize 
angle, I. P. will gladly oblige. 

Important N. Y. Decisions on 
L. U. Expulsions for Cause 

Suit of two members, expelled for work- 
ing an unfair job, against Newburgh, N. Y., 
Local 45, asking $5,000 damages each and 
reinstatement, was dismissed recently in 
N. Y. Supreme Court. Plaintiffs contended 
Local 45 had brought them to Newburgh 
from jobs in another town, that their expul- 
sions violated Union by-laws, and that they 
suffered monetary loss because of their in- 
ability to follow their profession. 

Trial testimony adduced the fact that the 
theatre had been picketed, and that the 
plaintiffs had been summoned before the 
Local executive board and informed that 
they invited expulsion by continued employ- 
ment at the unfair theatre. Said the court: 

Decision Upholding Expulsions 

"They (the plaintiffs) knew of the situa- 
tion, knew that the theatre had defied the 
Union, and by their continued employment 
were giving aid and comfort to the enemy 
of the Union . . . There is no question that 
the proprietor of the theatre refused to 
enter into any agreement with the Union, 
and that the plaintiffs, members of the Union, 
nevertheless persisted in working at the 
theatre, although they knew it had been 
declared unfair and knew that Union was 
opposed to their working there. 

"It is quite apparent that at the time 
the plaintiffs felt independent of the Union, 
were satisfied with their positions, and had 
no intention of recognizing any obligation 
to the Union." 

McGuire, Finn Named Honorary 

Members of British Guild 

P. A. McGuire, of the International Pro- 
jector Corp., and James J. Finn, editor of 
I. P., have been elected honorary members 
of the Guild of British Kinema Projection- 
ists and Technicians, the representative pro- 
jection craftsmen organization in England. 
Messrs. McGuire and Finn are the only 
American members of the Guild. 

FIGURE 1. Volume control amplifier 


U. S. District Court at Philadelphia has 
dismissed the suit brought by E. J. Vallen 
and Vallen, Inc., against Automatic Devices 
Co. for alleged infringement of patents 
covering automatic curtain controls. Costs 
were assessed against the plaintiff. 



Process Projection Specifications 


THE appended report of the Process Projection Equip- 
ment Committee of the Academy of M. P. Arts & 
Sciences presents, for the first time, the coordinated 
viewpoint of the majority of the Hollywood studios on this 
subject and should prove a valuable addition to the indus- 
try's technical literature. Process projection methods con- 
tinue to become increasingly important: 

Economically, they offer opportunities for still greater sav- 
ings in production costs. 

Technically, developments in equipment and technique con- 
tinue to expand the possibilities in this field until, some 
day, it will be the exception, rather than the rule, to send 
a cast on a distant location. 

Artistically, as this equipment and technique is further 
developed the extent of its use will be limited only by the 
imagination of the production personnel; whereas, up to 
the present time, the equipment has been the limiting factor 
and only the ingenuity and resourcefulness of the tech- 
nicians have made its wide use possible. 

In a foreword to the report, Farciot Edouart, chairman 
of the Academy committee, states: 

"Since the very inception of transparency process pro- 

jection methods, it has been found in general that available 
projection equipment for this type of work is principally 
composed of an assembly of units never originally designed 
in their entirety nor engineered to be combined and worked 
together in such capacity. Basic elements of these assem- 
blages were never intended to fulfill and meet such strict 
requirements as have been imposed upon such equipment 
by the consistent demand for higher quality rear projection 
results, and of the ever increasing scope required in the 
present stage of the motion picture art. 

"These recommendations are based upon Maximum Light 
Delivery with the following primary requisites: Absolute 
Steadiness of the projected picture with a Minimum of Light 
Variation on the screen, and Increased Efficiency of the 

"The designer and manufacturer should regard any 
tolerances affecting these three principles as concessions to 
practicability, and any method of decreasing these con- 
cessions will be considered definite advancements in design." 

The report, to be published herein in two instalments, is 
appended hereto: 



The base shall be so designed that it 
provides: (1) A rock-like stability dur- 
ing operation, when locked off, and 
facilities for panning and tilting with 
absolute smoothness and precision; and 
(2) sufficient portability so that the 
whole equipment may be easily moved 
about on its special carrier or dolly on 
the recording stage by not more than 
two men. 

(Auxiliary) : It has been suggested that 
this portability be accomplished by the use 
of a special carrier or dolly of the four- 
wheel type (on which the base will be 
mounted) equipped with solid rubber tires 
to insure safety and stability during move- 
ment of the equipment. The wheels should 
have the ability, free from any side-play or 
sway, to swivel and lock off in any direc- 
tion for possible dolly shots. To increase 
stability, suitable jacks should be provided 
to lift the equipment off the wheels for sta- 
tionary shots. Adequate bubble levels 
should be provided for leveling up the 


In the design of the base, provision 
shall be made for a free-moving and 
easily operated tilt and pan mechan- 
ism, giving a smooth movement when 
in operation, but including a positive 
locking device, giving locked - off 
stability equal to the stability obtained 
were this pan and tilt mechanism not 
provided. There should be no back- 
lash or Dlay whatsoever in the pan and 
tilt mechanism, and means for adjust- 
ment should be provided to keep all 
working parts tight at all times. (See 
"Rotation of the Projector Head.") 

(Accessory) : The design of the base 

should also provide for the addition, 
when required, of a variable speed mo- 
tor control of the pan and tilt mechan- 
ism, operating remotely from the camera 
position. The design of this remote 
control mechanism should provide for a 
gear ratio in the order of 900 to 1 between 
the drive motor speed and the speed of 
operation of the tilt and pan mechanism (to 
minimize over-control) as well as a gear 
box providing two lower gear ratios, mak- 
ing available all the necessary different 
speeds of operation. 


(Basic) : 

The base shall be designed to pro- 
vide an angle of pan of at least 15° 
to both right and left of the center line 
between the projector and the screen, 
making a total minimum horizontal 
coverage of 30°, and to provide an 
angle of tilt of at least 10° above and 

Classifications in Report 

In order to clearly specify the relative 
importance of the various recommenda- 
tions included in the report, each sub- 
heading in each part is indicated by one 
of the three following classifications: 

BASIC — Recommendations so in- 
dicated incorporate definite require- 
ments and principles. (Printed in 
bold face type.) 

AUXILIARY — Recommendations so 
indicated are suggested methods of meet- 
ing basic requirements. (Printed in 
light face type.) 

ACCESSORY — Indicates optional spe- 
cial refinements which add to the ease 
of operation of equipment. (Printed in 
italic type.) 

below the horizon, making a total mini- 
mum vertical coverage of 20°. 


The base shall be so designed as to 
allow for free, quick interchange of 
projection heads and lamphouses, 
registered with dowel pins or other 
positive means, so that a minimum of 
adjustment is required for lining up 
when a change in head or lamphouse 
is made. 

(Accessory) : In the event that devices 
other than the regular base previously men- 
tioned are provided to hold the projection 
head and lamphouse, the base on which the 
projection head and lamphouse rests should 
be designed so that projection heads and 
lamphouse are easily and quickly inter- 
changeable to such devices. 


The base shall include sound in- 
sulation to eliminate the transmission 
of noise. (It has been observed that 
sufficient sound insulation has been 
provided by insulating the setting jacks 
of the dolly with hard rubber. How- 
ever, it must be remembered that any 
material so used must not in any way 
detract from the absolute steadiness of 
the whole equipment.) (See "Maxi- 
mum Noise Level.") 


The base and special carrier shall be 
so designed that the equipment's 
optical axis, when parallel to the stage 
floor, shall be 5' 6" from the stage 


The type and size of carbon shall be 

MAY 193 9 


carefully chosen for maximum effi- 
ciency in relation to the selected type 
of optical system and lamphouse. 

(Auxiliary) : It is recommended that all 
motion picture producing companies and 
commercial organizations using process pro- 
jection equipment follow the manufacturers' 
rated burning conditions under wnich the 
maximum efficiency and minimum flutter 
and flicker are obtained from the carbon 
light source. (bee ""Light Control.") It 
is further recommended, to insure freedom 
from moisture or dampness, that carbons be 
kept for 48 hours before use in an electric 
heating oven operating at not to exceed 
125° F. 


Carbons for process projection shall 
be so selected by the manufacturer for 
straightness and concentricity of the 
core that when burned in a lamphouse 
developed and constructed to meet 
these recommendations, the equipment 
shall be able to fulfill the Tolerances 
under "The Feeding Mechanism," as 
well as the recommended "Tolerances 
in Light Variation of the Light Out- 


The current to the arc shall be so 
conducted into the lamphouse that no 
magnetic fields disturbing to the arc 
are set up. 

(Basic) : 

It is recommended that further de- 
velopment work be conducted on in- 
candescent and high-pressure mercury 
vapor lamps for general and special 
application to background process pro- 

POWER SUPPLY (Auxiliary): 

It has been suggested that a separate 
power supply be provided for the light 
source, inasmuch as a constant line voltage 
to the arc is imperative to accomplish the 
results to be obtained from equipment 
meeting these recommendations. 


The design of the whole equipment 
shall be such that the illumination 
from the carbon arc light source ap- 
proaches as closely as possible the 
steadiness of an incandescent source. 
In any event, the amount of light 
variation during the projection of a 
scene shall be less than ±2% per min- 
ute, but with a maximum of ±5% for 
any consecutive nine-minute shooting 

This tolerance is to apply only after 
a proper crater has been formed in the 


(Basic) : 

There are two distinct types of varia- 
tion in the light output of an arc lamp, 
which can be designated as "flicker,"* 
viz: a sudden sputter or brief increase 
or decrease in brightness, and as "fluc- 
tuation"* viz, moving in a slow wave 
of increasing or decreasing brightness. 

*NOTE: Flicker may be caused by the core 
of the positive carbon having different consist- 
ency in various spots, causing the arc to 

Panic, the Butcher 

This is a condensation of an article which originally appeared in Columbia, 

official organ of the Knights of Columbus, by whom it is copyright. It bears 

directly upon the problem of safety in the theatre, with which projectionists 

are so intimately concerned 

IT WAS the afternoon before Christ- 
mas, and in a small social hall in 
Calumet, Michigan, a woman's club 
was holding a party. The building was a 
two-story brick structure with the meet- 
ing place on the second floor, reached by 
a single six-foot-wide stairway. After a 
while the lack of ventilation, the crowd, 
and the steam heat began to make the 
room stuffy, and one of the women 
fainted. Somebody near her called for 
water. Somebody else, not so near, 
noticed the confusion, and, for some in- 
explicable reason, screamed "FIRE." 
And the consequence of that bit of 
thoughtlessness was the slaughter of 73 
of the women in that little hall only ten 
feet above the street! 

The firemen arrived a minute or so 
after an outsider turned in an alarm. By 
that time the bodies on the stairway were 
piled so high that the men had to throw 
ladders up to the window to get in. And 
when they raced to the head of the stairs, 
they found two elderly women in a frenzy 
of hysteria, jumping up and down madly 
on the stack of dead and dying! 

• Fail to Note Exits 

Similar things have happened many 
times and, in all probability, will happen 
again. In Baltimore 40 people died in a 
theatre crush over a false alarm fire; in 
Ville Platte, Louisiana, 27 were killed in 
a panic caused by a trickle of smoke; 
and in a Montreal movie house 78 chil- 
dren were trampled to death. The last 
was a real fire — but in the most notorious 

panic of modern times, the Iroquois 
Theatre disaster of Chicago, 572 persons 
lost their lives in a blaze which did only 
nominal damage to the building itself. 

Thus can panic produce butchery even 
without the aid of fire. The reason why 
sane people become maniacs in a crisis 
is that they never stop to think what 
they might do should an emergency arise. 
How many really "look for the nearest 
exit" before they settle themselves for 
the show? How many on going to a 
hotel for the night ever think about the 
business of getting out in a hurry? Very 
few. The upshot is exactly the same in 
every public fire we have: all the occu- 
pants attempt to go out the same way at 
the same time — they go out the same way 
they came in, which is the only way they 
know — and that pathway promptly be- 
comes congested. One impatient shove, 
one excited scream, and a taut crowd 
becomes a savage pack of animals. 

The first sensible rule is never to go 
into a theatre or public building without 
due thought to the matter of exit. Notice 
especially, a second path of escape — the 
nearest side aisle in the theatre, the 
stairway at the other end of the hall in 
the hotel, etc. Fix it firmly in your mind 
If an emergency arises, use that path of 
egress for yourself and your family be- 
cause you can be positive that nine-tenths 
of the others in the building will try to 
utilize the main entrance. 

A few years ago ten girls were killed 
in a movie studio fire in New York pri- 
marily because they failed to look for a 
second exit before it was needed. Their 

momentarily sputter, or by sudden air drafts 
or misdirected magnetic flux, or by misalign- 
ment of the negative carbon with respect to the 

Fluctuation is a mechanical or electrical prob- 
lem and is caused by off-center rotation of 
the crater, the carbon feeding in an irregular 
manner, a crooked carbon, or disturbances in 
the line voltage. 

MENT (Basic): 

Flickers are generally too fast to be 
measured by any presently known 
meters, but shall be measured by 
photographing a clear screen illum- 
inated by the arc lamp source. Each 
frame of the exposed, developed nega- 
tive, over given portions, can then be 
read on a densitometer.* 

UBEMENT (Basic): 

Fluctuation can be easily read and 
recorded with an accurate, sensitive 
light-recording photometer. 

*NOTE: It is recognized that this method of 
measuring flicker may not be the most accurate, 
due to variations in film development, but is 
one simple means available at present. The 
Committee will welcome suggestions on more 
accurate methods which may be devised. 


General Recommendations Applying 

To Both Mirror and Condenser Type 



(Basic) : 

Recommendations covering capacity 
and optical speed for each type of 
lamphouse are given in that Section of 
this Part of the Report specifically 
applying to each type of lamphouse. 


The noise level of the lamphouse in 
operation shall be 3 db below the noise 
level specification given for the whole 
equipment in that part ("Noise 
Level") of these recommendations. 
This specification must be met with- 
out the use of booth or blimp on the 

(Auxiliary) : It has been suggested that 
acoustic treatment of the lamphouse might 
prove effective in meeting the above basic 
noise level recommendations. 

(Continued on page 24) 



dressing rooms were on the second floor, 
within easy reach of two supplementary 
paths of exit. But those girls had always 
come up by the main stairs, and they 
went out that way when they had to make 
a quick escape. The stairway was a 
roaring oven when they attempted it. 

Wide-awake cities commonly provide 
that in a theatre "no seat shall be more 
than seven seats from an aisle." And 
when theatre managers know their busi- 
ness they see to it that ushers lead as 
many possible to their seats by side aisles 
instead of down the main one. Perhaps 
you have wondered at times why the 
usher made you crawl over the knees of 
five others when it would have been eas- 
ier to have gone down the main aisle: 
they are trying to divert a maximum of 
traffic away from that aisle against the 
ever-present contingency of emergency 
egress. Common sense behavior in a 
public place is to expect the worst and 
formulate some tangible plan of action 
before it happens. The result is that you 
automatically do the right thing because 
the danger is not unexpected: 

But, to be sure, not all of the ghastly 
record of panics can be charged to the 
behavior of the victims. If there aren't 
any supplementary exits, if doors won't 
open, if stairs are unprotected or too 
steep or have sharp turns, you can't 
expect undisciplined people to do any- 
thing but lose their heads. The second 
antidote for panic, then, is to be found 
in common sense fire regulations. Though 
many building owners object to the pro- 
visions of fire codes, they object because 
they have no conception of the problem 
involved. While the owner racks his 
brain for ways to "get them in," some- 
one else has to worry about the more 
vital problem of getting them out. 

This failure of owners to appreciate 
the risks of panic leads to many atrocious 
violations of existing codes — or to the 
total neglect of safety principles where 
no codes exist. Thousands 'of cases 
comparable to the following come to 
light every year. 

• Movie House Deficiencies 

A few months ago an inspector found 
a brand-new movie theatre in a New 
England city equipped to seat 5000 
patrons. When he asked to see the sup- 
plementary exits, they pointed to a red- 
lighted door up near the stage and when 
he opened that door he discovered that 
it led to a ten-foot drop to the river be- 
low! Another exit on the side was ex- 
amined. That was seven feet above the 
street — and there were no steps. Despite 
these conditions, a check-up showed that 
they were packing 7500 patrons in a 
place designed to hold 5,000! 

In another theatre the owner was com- 
pelled to add a secondary exit when it 
was discovered that none had been pro- 
vided in the original plans. This was 
done willingly enough when the need was 
explained — but where do you suppose 
they built it? At the side of the build- 
ing furthest from the street, leading into 

a four-and-one-half foot light shaft 
entirely surrounded by the adjoining 
building. From this trap, which would 
hold about 20 persons, there was no es- 
cape for any of the 2,000 patrons who 
might use it! 

• Closer Inspection Urged 

The only solution for such stupidities 
— which are by no means rare — lies in 
relentless activity on the part of the local 
fire department, intelligent ordinances, 
and rigid inspections backed up by ag- 
gressive public opinion. For if the 
people themselves aren't concerned with 
their own safety, no one else will be. 

All these warnings apply to non-pro- 
fessional social assemblages, which in- 
variably present a far greater hazard 
than the worst public places. The frat- 
ernal or club gathering, the amateur play, 
the crowded meeting in church hall or 
school — these affairs are of temporary 

duration and are managed by folks who 
have no knowledge of the fire problem 
and little legal obligation. The curse of 
all these gatherings is the common use 
of chairs that are not fastened to the 
floor or at least made into rigid units of 
five or six seats. At the first sign of 
trouble, chairs are tipped over, aisles 
blocked, and excited people begin to fall 
right and left. 

Another danger is the lack of checking 
facilities for coats and wraps which are 
carried into the meeting place and draped 
on chairs whence, at the earliest outbreak 
of confusion, they fall to the floor to 
be tripped over. It should be an ironclad 
rule to have ample check rooms. Be- 
yond these elementary risks there are 
dozens of others. Aisle space is reduced 
to an absolute minimum and no regard 
whatever is paid to the importance of 
keeping exits and fire escapes unob- 

Weber Announces Syncro-Magnetic Soundhead 

Weber Machine Corp., of Rochester, 
N. Y., pioneer independent sound equip- 
ment manufacturer and contributor of 
many notable advances to the art, has 
announced a new Syncro-Magnetic sound- 
head which employs a patented magnetic 
filter having approximately 40 pounds of 
"flywheel" balance. All of the starting 
load and shock has been eliminated, ac- 
cording to Weber engineers, and the new 
head starts more gently and maintains as 
perfectly a uniform motion as is humanly 
possible to obtain. 

In thus solving the problem of constant 
speed, Weber claims not to have sacri- 
ficed a single detail that makes for im- 
proved performance, trouble-free opera- 
tion and convenience. 

• Advanced Optical System 

The optical system of this new head 
is of the very latest improved design, 
running up to 10,000 cycles, and is easily 
and quickly focused. Lateral adjustment 
of the film is provided for to accommo- 
date any variation of the sound track 
from standard. The secondary optical 
system is easily adjustable, and it can 
be speedily replaced with one for push- 

pull or any other advanced type of re- 
cording. Pre-focused exciter lamps 
mounted on a turret can be put into 
service by merely flipping a lever. 

Film is easily threaded into the sound- 
head. All sprocket roller levers are 
rugged and self-locking. Ample room 
and accessibility arc provided for the 
projectionist, and the pilot light has a 
separate switch. All bearings are high- 
grade ball bearings, and no oil is nec- 
essary at any time. 

Further details of this new Syncro- 
Magnetic soundhead are available from 
the manufacturer at 59 Rutter St., 
Rochester, N. Y. 


James Frank, Jr., has been named Man- 
ager of the N. Y. City branch of National 
Theatre Supply Co., succeeding C. H. Secor, 
resigned. Previously Frank was assistant 
sales manager of International Projector 
Corp. and with the sales promotion section 
of N. T. S.; before that he was for eight 
years with RCA. 

Frank is Secretary of the S. M. P. E. and 
is well known for his articles on sound en- 
gineering, notably those appearing in I. P. 
under the name of Frank T. Jamey, Jr. 

Weber's new Syncro-Magnetic soundhead 

MAY 1939 


Film Preservative Tests 


TREATMENT given to release print 
film after it has been printed, de- 
veloped and dried is commonly called 
"film preserving," and the processes by 
which this treatment is given are known 
as "film preservative" processes. 

The gelatin of freshly developed film 
carries a high percentage of moisture 
in its pores, and as long as this condition 
prevails is known as a "green" emulsion. 
A so-called "green" emulsion is quite 
soft and the slightest abrasion will cause 
a scratch. These scratches widen out 
as the gelatin dries, and cause the 
"rainy" effects seen on the screen in the 

As film with "green" or soft, emulsion 
passes through a projector, it leaves 
small deposits of emulsion on the tension 
shoes at either the aperture plate or the 
sound gate,, unless the tension shoes are 
Tcept thoroughly lubricated. Such de- 
posits build up resistance to a free pas- 
sage of the film over them, and scratch 
the film during projection. 

When the moisture in a "green" emul- 
sion is withdrawn too quickly, the gela- 
tin shrinks and the film warps or buckles. 
If too great an amount of moisture is 
-withdrawn from the gelatin, the film be- 
comes brittle, loses its pliability and is 
easily torn while being projected. 

Any treatment offering a preventative 
of the above conditions must be applied 
to the film after it has been printed, de- 
veloped and dried. A film preservative 
treatment for release prints should: 

(1) Prevent scratches in new or green 
emulsion. .'..'.' •', 

(2) Thoroughly lubricate the emul- 
sion so that it will not adhere to any 
part of the projector. 

(3) Impregnate the gelatin with a 
fixed chemical which will not be dissi- 
pated by the intense heat of the projec- 
tion lamp, but will take the place of the 
moisture that is withdrawn to thus pre- 
vent warping and buckling. 

(4) Retain the film's pliability indefi- 

• The Test Procedure 

It was decided that a comparative test 
of the commercially available preserva- 
tives could best be made by including in 
one reel a sample of release print treated 
by each of these processes, and subse- 
quently subjecting this test reel to re- 
lease print film projection under actual 
theatre conditions. 

A 2000-foot reel of film was secured 
from a regular release, cut into 200-foot 

samples and each sample subsequently 
treated by one of the following preserva- 
tive processes: 

Consolidated edge waxing. 

Eastman cold waxing. 

Gage process. 

Metro-Goldwyn-Mayer edge waxing. 

Paramount process. 

Peerless process. 

Perfexit process. 
The reel also included one 200-foot sam- 
ple of unprocessed release print*. 

This test reel was then subjected to 
approximately ten months actual theatre 
use. The reel was projected in all types 
of theatres, — first, second, third run city 
theatres, and subsequent run neighbor- 
hood houses, so selected that the reel 
would be projected in theatres equipped 
with all types and makes of projection 

This film was mounted on a standard 
commercial 2000-foot reel and was trans- 
ported from theatre to theatre in a reg- 
ulation I.C.C. shipping case by various 
available commercial transportation fa- 
cilities. It was received and handled by 
the theatre projectionist in exactly the 
same manner as an ordinary release print 
and was projected in each theatre from 
two to six times (depending upon the 
time available in each particular theatre 
for this test), upon each of the project- 
ors installed in each theatre. 

In other words, the reel was subjected 
as closely as possible to the conditions 

*It should be noted that the above listing of 
processes tested is alphabetical and bears no 
relation to the order of listing in Table A. 

to which an ordinary exchange release 
print is subjected. 

Under these conditions, the reel was 
projected a total of 439 times. The film 
was then examined (1) being inspected 
by projection (2) cleaned and repro- 
jected (3) inspected by hand (4) meas- 
ured for shrinkage and (5) tested for 
surface hardness. 

• The Analysis Procedure 

This analysis indicated the following 
conclusions: The first inspection by pro- 
jection showed the film to be filled with 
dirt, scratches and oil, and each of the 
samples appeared to be in very poor con- 
dition. The first and last samples on the 
reel were in the worst condition, as would 
be expected, due to the handling of the 
film in threading and rewinding. 

After the Test Reel had been cleaned 
several times and reprojected, the con- 
clusions from the first observation were 
revised because of the fact that the 
true condition of the film was obscured 
by dirt and oil. The film was in much 
better condition than was first indicated. 
The amount of oil on the film was more 
objectionable than the scratches remain- 
ing on the film after cleaning. 

The tabulation in Table A shows the 
results of the various observations in a 
fairly concise form. Shrinkage meas- 
urements were made with the Paramount 
Film Gauge. This gauge is accurate 
to within .001" in 3', and has been cali- 
brated against both the Eastman and 
Dupont gauges. 

The hardness test was made by draw- 
ing the film between a flat surface and a 
steel point with adjustable weights, set 
to provide various pressures. A certain 
pressure is applied on the steel point 
and increased until the steel point starts 
abraiding the film. The good samples, 
with 3 pounds of weight on the steel 


tilts of various 

observations on test reel 


Before Cleaning 

After Cleanina 


Center Edge 

in 1 Foot 

Sample No. 1 

Dirty and pitted, 
particularly at 

Fairly free of abra- 
sions, except begin- 

Beginning badly 
pitted and short 

Fair. Good. 


Sample No. 2 

Fairly clean. 

Fairly free of any 
noticeable abra- 

Less scratches than 

Poor. Good. 


Sample No. 3 Fairly clean. 

Fairly free of any 
noticeable abra- 

Long scratches in 
center of film. 

Poor. Good. 066" 

Sample No. 4 Dirty and pitted. 

Fairly free of any 
noticeable abra- 

Long scratches in 
center of film. 

Poor. Good. .067" 

Sample No. 5 

Dirty and pitted. 

A few long scratches 
in center. 

Better than No. 3 
and No. 4, but some 
short scratches. 




Sample No. 6 

Fairly clean. 

Fairly free of abra- 

Some long scratches 




Sample No. 7 


Dirty and pitted. 

Long, heavy 

Long scratches 
heaviest on this 




Sample No. 8 

Beginning good, 
end full of short 

Beginning quite 
free of abrasions. 

Fair. Good. .057" 



point, slid easily through without any 
emulsion abrasion; whereas the poor 
samples received deep gouges. 

The hand inspection showed that all 
the samples have perforation nicks 
throughout, due to pulling in the pro- 
jectors. Some of the samples appeared 
to have less lengthwise scratches than 
others, which seemed to be the main dif- 
ference between the various samples. 

• Summary of Findings 

After inspection of the samples it 
would be rather difficult to point out any 
one sample as outstandingly better than 
the others. Samples 2, 3, 4, 5, and 6 
appear to be in the best condition, then 
7. Samples 1 and 8 are about 
as good as the first group, except for the 
beginning of 1 and the end of 8, which 
sections are by far the worst of any of 
the samples. 

It is interesting to note that the edge 
of all the samples show equally well in 
the hardness test, the main variation 
being in the center of the frame. The 
greatest benefit from any of the preserva- 
tives is probably at that period when the 
film is green, as a preservative will per- 
mit projection without chatter in the 
projector gate. However, after the 
samples become old, the natural harden- 
ing of the emulsion and glazing by the 
projection shoes tends to equalize the 
differences along the edges of the film. 

The last sample was not on the reel 
the same length of time as the rest of the 
samples, having been added some weeks 
after the Test Reel was originally made 
up. For this reason, the shrinkage fig- 
ures are, and should be. somewhat small- 
er than those found in the other samples. 

The sound track area of the various 
samples did not seem to suffer any more 
than the picture, but the background 
noise was probably higher than when the 
film was new. For the information of 
those interested, the following is a sample 
formula for an edge waxing solution: 
50 oz. Trichlorethylene 
50 oz. Benzol 
7 oz. Parowax 
2 l A oz. Pyroil "B" Grade 

• Committee Recommendations 

These tests indicate that because of 
the fact that a film preservative con- 
tributes to better projection as well as 
longer life, all release prints should be 
given some treatment before being 
placed in use. It is further recom- 
mended that in order to obtain full bene- 
fit from a preservative, any preservative 
used should be applied at the laboratory 
during the release printing procedure. 

However, the results of this one test 
indicate that all of the preservatives 
tested benefit the film, and in the opinion 
of this Committee there is little difference 
between the results obtained from any 
one or the other of the various preserv- 

New Erpi Mirrophonic ^Master' 
Theatre Sound System 

EMPHASIZING the trend that has 
featured many recent sound equip- 
ments, Electrical Research Products' new 
Mirrophonic Master system, exhibited 
recently, was designed and built around 
the two principles of maximum simplic- 
ity and accessibility. 

New developments of special interest 
to projectionists center largely about the 
soundhead, the film side of which is 
shown in Fig. 1. It will be noted that 
the exciter lamp and . the photocell are 
now at the same side of the head, the 
lamp on top and the cell beneath. The 
basic optical arrangements are plainly 
shown in the illustration. 

• Utilizes Single Sprocket 

The drum on which the film rides as 
it passes the exciting light is that of the 
kinetic scanner, modifications of which 
are confined to the drive side of the head, 
and discussed subsequently. 

The most unusual feature of the oper- 
ating side is the use of a single sprocket 
to provide that protection against flutter 
usually afforded by two sprockets. This 
sprocket is oversize; it will be noted that 
the film is threaded against the upper 
circumference and held in place by idler 
rollers; then follows a short loop and 
the film is returned to the lower cir- 
cumference, and another set of idler 
rollers. The length of film and the 
number of sprocket holes engaged are 


about the same as though two sprockets 
of ordinary size were used, but the gear 
train is, of course, simpbfied, thus en- 
abling greater economy and reduced 
chances of trouble. 

The rotating elements of the kinetic 
scanner are hermetically sealed in the 
Master system, and utilize a new liquid. 
The principle of action is unaltered; the 
drum seen in Fig. .1 is an extension of 
the outer rotary unit, which contains 
within itself a flywheel from which it is 
separated only by a film of liquid .0001 
inch thick. When the motion of the film 
sets the drum rotating, the motion is 
imparted to the inner flywheel through 
the liquid contact on a principle some- 
what similar to that of a friction clutch, 
and the flywheel, once it is moving, 
steadies the rotation of the drum. 
• Driving Arrangement 

Stability of operation at all tempera- 
tures, however, requires that the coupling 
liquid shall not change greatly in vis- 
cosity when warmed or chilled. In the 
new scanner, the fluid used is one speci- 
ally developed for the purpose by Bell 
Telephone Laboratories and said to cost 
$200 per gallon. Hermetic sealing of 
the unit insures that the trifling quantity 
originally built-in will never have to be 
replaced. Its stability in suppressing 
flutter at all temperatures is reported as 
ten times greater than that of any 
liquid previously used for the purpose. 

Other soundhead features include the 
{Continued on following page) 

atives which were under consideration. 
Due to the fact that new film preserva- 
tive processes will be developed from 
time to time and changes in existing 
processes will likely be made, we recom- 
mend that additional tests similar to this 
be made as necessary, and if so desired 
this Committee will be glad to conduct 
such tests. 

In conclusion, the Committee wishes to 
acknowledge with thanks the helpful 
cooperation of Ferdinand Eich of the 
Paramount Studio Laboratory, who con- 
ducted much of the investigation outlined 
in the foregoing report, and of the man- 
agers and projectionists of the many 
theatres who cooperated in the tests upon 
which this report is based. 

MAY 1939 


mounting of the motor at the side, which 
leaves the armature in horizontal posi- 
tion at all projection angles. Lubrica- 
tion leakage is reduced, and the motor 
requires no thrust bearings. 

Drive linkage to the projector is by a 
silent chain; the head in consequence is 
more easily aligned. An improved mount- 
ing plate further facilitates alignment. 
Projector heads can be changed between 
reels and still be perfectly mounted. 

Soundhead wiring terminals are shown 
at the extreme left of Fig. 1. The 
ground terminal is at the top; the next 
pair, reading down, are Exciter — and 
Exciter + ; the next stud is the 90-volt+, 
and the bottom pair, bridged by a re- 
sistor, carry speech output to the coaxial 

Speech from both projectors is run 
to a three-stage pre-amplifier (Fig. 
2), with exciter lamp resistors at the 
bottom of the cabinet. The right side 
of the cabinet carries, at the top, the 
changeover switch, and beneath that, the 
volume control. Contacts of both switch 
and control are of the commutator type, 
the "brushes" being phosphor-bronze 
spring contacts. 

The amplifier chassis at the middle of 
the cabinet of Fig. 2 resembles a radio 
chassis that has been turned on its side 
to make all the wiring accessible. Every 
contact and connection can be reached 
with the amplifier in this normal oper- 
ating position. Resistors are not marked 
with numerical ratings, but, as may be 
noted in the illustration, are color-coded. 
Tubes are Western Electric. 

Speech from the pre-amplifier is wired 
to the system amplifier, which has a 
meter panel that is readily removable by 
the loosening of two screws: it can be 
set at the bottom of the cabinet with its 
cable form still connected for continued 
meter operation during the course of 
servicing. When this is done, the ap- 
pearance of the amplifier resembles that 
of Fig. 2 — a radio chassis set on end with 
every connection exposed. 

Terminal strips for external wiring are 
visible along the bottom of its chassis; a 

New DeVry 16 mm. Projector 
For Theatre Use 

A new 16 mm. projector which utilizes 
a high-intensity carbon arc lamp was in- 
troduced recently by the DeVry Corp. 
and created unusual interest among pro- 
jection men. The unit, intended for 
projecting local newsreels in regular 
motion picture theatres, incorporates all 
of the essential 35 mm. mechanical re- 
quirements necessary for heavy-duty use, 
including a sprocket intermittent instead 
of the ordinary amateur claw-type system 
commonly found in 16 mm. projectors. 

A unique system of forced draft ven- 
tilation has enabled continuous test runs 
of 50 hours without overheating the unit. 
The projector has a capacity of 4000 feet 
of 16 mm. film, sufficient for a run of 
VA hours. Complete details available 
from the company at 1111 Armitage 
Ave., Chicago. 


line of resistors at its top, left, are for 
modification of frequency response. 

• Amplifier Rating, Hook-up 

The amplifier is resistance-coupled 
throughout, with phase inversion to the 
push-pull stage. Output is rated at 15 
watts with 2% distortion. Its meter is 

calibrated in terms of percentage. The 
switch for reading different circuits is on 
the meter panel, the monitor volume 
control at its right. A separate, single 
stage is included for monitor sound sup- 
ply, eliminating variation in screen 
speaker volume when the monitor control 
is adjusted. The design contemplates 
use of two of these amplifiers in parallel, 
when necessary, and the addition of a 
Mirrophonic 87-type amplifier (I. P. for 
Dec, 1936) for still greater volume. 

The system includes a tube rectifier 
power unit, an interesting special feature 
of which is the use of a voltage regulator 
tube to stabilize the exciter lamp supply. 
It is simply a lamp with a long filament, 
the resistance of which increases, of 
course, with temperature rise. This fila- 
ment is in series with the output line; 
increased current through it, raising its 
temperature, results in increased filament 
resistance, and vice versa. These com- 
pensating changes in the filament voltage 
drop stabilize the voltage at the output 
terminals against fluctuations of line cur- 
rent or of rectifier action. 

Loudspeakers of the Master system are 
of the Mirrophonic type previously used. 

Erpi will first market this new equip- 
ment abroad. An announcement cover- 
ing merchandising arrangements in the 
United States is expected in the very near 

New Projectors by Brenkert, Wenzel; Forest Lamp; Brenkert- 
RCA Sales Tieup Highlight Radical Supply Field Changes 

RECENT radical changes in the man- 
ufacture and merchandising of pro- 
jection room equipment merit the atten- 
tion of projectionists. Most interesting 
development in the manufacturing field 
is the introduction of a new 35 mm. pro- 
fessional theatre projector by the Brenk- 
ert Light Projection Co., of Detroit, well- 
known in the field as the makers of 
Brenkert arc lamps, effect machines and, 
until recently, rectifiers. 

No detailed information anent the 
Brenkert projector is available to date, 
although it is known that many units 
are ready. Brenkert states that they 
have been tooling up for this job for the 
past two years. 

Of extreme interest is the merchandis- 
ing plan which becomes effective with 
the introduction of this new projector. 
Brenkert announces that the head will 
be handled by Brenkert dealers through- 
out the country; and that a deal has been 

N. Y. World's Fair Visitors 

Readers of I. P. who contem- 
plate visiting the New York World's 
Fair are cordially invited to avail 
themselves of the facilities of the 
I. P. office in the matter of hotel 
accommodations, reservations for 
amusements or for any chore which 
will help to make their visits more 
enjoyable. Ample advance notice is 

worked out with RCA Photophone where- 
by the latter will cooperate with Brenkert 
dealers in all sales and servicing efforts. 
Thus, a given dealer will be able to 
equip a projection room complete: the 
dealer will have the right to offer RCA 
sound units, and RCA will have the right 
to offer visual projection equipment. 
Ample financing on sales is reported set. 

Currently many dealers are handling 
both Brenkert lamps and Motiograph 
projectors, thus there will be inevitably 
some radical switches in policy pending 
the final dealer alignment. Moreover, it 
is expected that Altec Service Corp. 
will stand idly by in the face of the wide 
competitive advantage enjoyed by RCA 
in the service field through its tie-up 
with Brenkert. 

Also closely tied-in with the Brenkert 
distribution setup is the Benwood-Linze 
Co. (formerly B-L Electric Co.), of St. 
Louis, which has taken over the Brenkert 
rectifier, made certain changes therein, 
and will market through Brenkert deal- 
ers, and the Robin Steadypower gener- 
ator. The addition of a screen manufac- 
turer to this group would not be sur- 

• Wenzel Head; Forest Lamp 

Another professional theatre projector 
will shortly be made available by the 
Wenzel Co., of Chicago. It is under- 
stood that a development by two Detroit 
projectionists forms the basis for this 
new Wenzel job, details of which are 



expected to be forthcoming shortly. 
A new Suprex lamp to be ready within 
thirty days is announced by Forest Mfg. 
Corp., of Belleville, N. J., which already 
sponsors the Forest magnesium copper- 
sulphide rectifier and the Hurley sound 
screen. No data anent this new lamp 
have been released as yet, although 
Forest asserts that it will uncover a 
radically new means for arc feed control. 

I. A. Revokes L. 37 Charter, 
Forms Five New Locals 

The charter of Local 37, largest I. A. 
unit with more than 6000 members, has 
been revoked by the General Office, and 
in its stead five new locals have been 
formed to accommodate the various clas- 
sifications of workers. This drastic 
move climaxed the almost uninterrupted 
warfare — including numerous court 
battles, physical violence at meetings, ap- 
peals to the Federal government by both 
sides and general confusion — which has 
marked relations between the Interna- 
tional and its West Coast studio workers. 

Dissolution of Local 37 was ordered on 
the eve of superior court hearings on 
suits filed by the International and Local 
37 against each other for control over 
the Local. 

The International avers that its actions 
are directed at ridding its studio affiliate 
of Communistic and other subversive 
elements; while Local 37, through offi- 
cials ousted by the I. A., sets as its goal 
the restoration of local autonomy. 

New units chartered by the I. A. to 
supplant Local 37 are: Local 80, all 
grips and special effect men; 44, labor- 
ers and utility workers; 727, studio pro- 
jectionists; 165, all handlers of electrical 
apparatus, and 728, recording men. 

Ed Cahill Heads Photophone 
Div. of RCA; Keeps Service 

Ed Cahill, director of service opera- 
tions for RCA Mfg. Co., has been as- 
signed additional duties as general man- 
ager of the entire Photophone division 
of that company. Harry Sommerer, 
former manager of Photophone, has been 
named assistant to the executive vice- 
president. Homer Snook will continue to 
direct Photophone sales. 

Cahill is well known to hundreds of 
projectionists throughout the country as 
a result of his activities in the servicing 
field. Before going to Camden he hand- 
led RCA service in the Chicago area. 


Bill making compulsory the employment 
of a projectionist for each projector used 
in theatres in N. Y. City met with a stun- 
ning defeat in Assembly recently, being 
licked by a 81 to 33 vote. I. A. legislative 
representatives openly predicted victory by 
a close margin. 



Moderately improved operations will be 
experienced by the motion picture industry 
during the second quarter of 1939, although 


Chief Projectionist, Detroit United Theatres, 

Detroit, Michigan 

Inspectors' Visits 

Welcomed, Declares 


Chief Projectionist 

.o maintain high standards of sound projection is an increasingly im- 
portant job in motion picture theatre operation today, as a result of the 
fact that new technical advances in sound recording have been coming 
thick and fast in the last few years, and will undoubtedly continue to do so. 

"The projectionists in our theatres, and the Altec inspectors who visit 
our projection rooms regularly, take a sincere personal interest in making 
the product shown in our theatres come through with every last drop of 
entertainment value for the patrons. 

"Altec engineers have proven themselves very competent in handling 
our many technical problems. As an example, these involve the ever- 
increasing necessity for applying additional amplifier power wherever re- 
quired, plus the need for improved equalization. The application of these 
technical developments along with a number of other Altec ideas has 
directly effected an improvement in the sound reproduction and distri- 
bution in our theatres." 


2 50 West 5 7th Street • New York City 

MW 193 9 


There Are I 
of All 

for All 

For projection you can use nothing 
better than STRONG 


They provide more light at less cost 
per unit — the steady, brilliant, snow- 
white light essential to proper pro- 
jection of color pictures. 

For sale by Independent Theatre Supply 
Dealers everywhere. Demonstration without 
obligation. Write today for free catalog on 
Strong unconditionally guaranteed products 
. . . your guide to better projection. 




2501 Lagrange Street Toledo, Ohio 

Export Office: Room 2002, 220 W. 42nd St. 

New York, N. Y. 

theatre attendance and box office receipts 
are expected to hold at levels only slightly 
in excess of last year, according to Poor's 

Contrasting with this fairly satisfactory 
outlook, a combination of political factors 
yre disturbing, the survey continues. In 
addition to the Department of Justice's anti- 
trust action are (1) the Neely "block-book- 
ing" bill, now before the Senate Interstate 
Commerce Committee, and (2) threats of 
National Labor Relations Board hearings 
on wages, strikes, and union activities. At 
this juncture, it is difficult to forecast the 
ultimate outcome of current and pending 

As for "block-booking," arguments pro 
and con seem to be pretty well in balance. 
Whether its elimination ultimately would 
prove beneficial to the industry is anybody's 
guess. Increased competition and higher 
production costs would be a natural conse- 

Theatre Construction Off 

With prospects indicating no important 
increases in theatre attendance, the incen- 
tive for building new film outlets has been 
dampened in recent months. Extending the 
decline experienced during 1938, contract 
awards during the first two 1939 months 
were nearly 45% under those of a year 
earlier, with February, 1939, registering a 
51% slump. Some improvement may be 
witnessed later this year, however, if the 
industry's prediction of another upswing in 
box-office receipts materializes. 

Reflecting the unsettled European situa- 
tion and recent years' rise in quota systems 
and other restrictive measures, exports of 
domestic films in January, 1939, were nearly 
15% under year-earlier volume, thus extend- 
ing the 10% decline under 1937 shown in 


The ninth annual National Conference of 
Visual Education, held under the auspices 
of the DeVry Foundation, will be held at 
the Francis W. Parker School, Chicago, 
June 19-22. The sessions will feature almost 
continuous showing of selected industrial 
and educational film, in addition to addres- 
ses bearing on equipment and technique. 


Convention of all I. A. locals in the 8th 
District will be held June 4-5 at the Port- 
age Hotel in Akron, Ohio. More than 100 

local delegates, plus international officers, 
are expected to attend. 


Roy Ruben was elected financial secretary 
of Local 199, Detroit, succeeding M. A. 
Hawkes, deceased; D. F. Erskine was 
re-elected v.-p.; Joseph Sullivan, rec. secre- 
tary, and H. S. Morton a trustee. 


Guercio & Barthel, theatre engineering 
and supply house in Chicago, will move 
early in June to their new building at 1241 
South Wabash Ave. 


Alan A. Cook, well known in the thea- 
tre field as a result of his work in pro- 
jection optics for Bausch & Lomb Co., 
has joined the scientific staff of the Wol- 
lensak Optical Co., Rochester, N. Y. He 
will specialize as a consultant and optical 


(Continued from page 18) 


The lamphouse shall be provided 
with a striker, hand or motor, which 
produces no detrimental magnetic 
effects on the burning of the arc ar"* 
which will not shatter the crater. 


Large adequate viewing ports shall 
be provided in both sides of the lamp- 
house, located at the most advantage- 
ous position. 


The lamphouse door shall open up- 
ward rather than outward (forward or 
backward) and shall be provided with 
a positive holding device when open. 
(It has been suggested that the lamp- 
bouse doors be of the type which fold 
or collapse into a smaller unit when 


(Basic) : 

Controls and meters shall be cen- 
trally located at one position on the 
operating side (the right side facing 
the screen) for ease of operation of the 

(gi£?ffli£ SAYS- 



cue at 40&/a6 &&ia£t&t 
CUtfl iJ~buf~iH£, cm. 40&/ unth 
t&t -&yi6 Hs&ti -fa tau) TvfiataM, 

V 1,0 It 






(except for special pur- 


The lamphouse should be adaptable to 
operation from either the right or the left 
side for special purposes. 


A small port shall be included in the 
rear housing of the lamphouse in line 
with the optical center of the equip- 
ment so that, with no carbon in the 
mechanism, preliminary lining up may 
be accomplished by sighting through 
the carbon jaws and aperture. 

ELEMENTS (Basic) : 

The burner elements, both the posi- 
tive and negative, shall be easily re- 
movable from the lamphouse in order 
to replace parts and to facilitate clean- 
ing, and shall be interchangeable be- 
tween Iamphouses of the same type. 

ASH TRAYS (Accessory) : 

Removable trays in the bottom of the 
lamphouse should be provided to catch 
debris and to facilitate keeping the lamp- 
house clean. 

GREE TILT (Basic): 

The design of the ventilating system 
shall be such that the ventilation will 
not be reduced when using the lamp 
at a maximum angle of tilt of 30° 
above or below the horizon.* 


The walls of both type Iamphouses 
shall be so designed and treated that 
the heat will be conducted through the 
chimney rather than radiated out 
through the side of the lamp, thus 
lowering the temperature of the lamp- 

(Auxiliary) : It has been suggested that 
should the lamphouse not be used with a 
portable equipment, a metal cover be 
provided over the upper part of the lamp- 
house with sufficient clearance to set up a 
draft between this cover and the lamphouse, 
to carry the heat transmitted through the 
himphouse up the chimney. 


(Basic) : 

AH parts of the lamphouse and shield 
(baffles) shall be constructed to dis- 
tribute the magnetic flux in a manner 
that will not disturb the proper burn- 
ing of the arc. 


(Basic) : 

An indicator shall be provided com- 
prising a compact, rigid optical system 
having a visual target index to show 
the burning relation between the car- 
bons. An indicator shall also be pro- 
vided to show the length of trim left 
in the lamp. 

An accurately calibrated and depend- 

*NOTE: In the opinion of the Committee, a 
30° angle is the maximum tilt at which it will 
he necessary to burn the lamp. This angle 
is greater than the minimum degree of tilt 
specified previously for the projector, hut may 
at times be reached in operation due to the 
equipment as a whole being purposely set off- 
level in some particular setup. 

MAY 1939 

Projection quality 


Good projection can influence box-office receipts. That's 
why it pays to project your pictures through a B&L Super-Cinephor 
Projection Lens. 

True anastigmats — the first to be offered for projection — 
produce images that are critically sharp right to the edge of even the 
largest screens. They are also fully color-corrected. 

Because your audience's eyes don't have to compensate 
for projection defects, they will enjoy the picture more thoroughly. 
With every show you make new friends — and one new patron a day 
will pay for a Super-Cinephor in a year. Write for details. Bausch 
& Lomb Optical Co., 616 St. Paul St., Rochester, N. Y. 



j . All New 

Announcing... ^^X 

For all projectors and sound equipments 

All take-ups wind film on 2, 4 or 5 inch hub reels. 

The Clayton Rewinder 

For perfect rewinding on 2000-foot reels. 


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BECAUSE ... They are the 
only rectifiers using tested P. R. 
Mallory Magnesium - Copper Sulphide 
rectifying units, whose immunity to 
projection room heat factors has been 

BECAUSE ... They meet suc- 
cessfully and efficiently the amperage 
requirements of today — even when two 
lamps or a spotlight must be operated 
from ONE Rectifier. 

BECAUSE ... The simplicity 

of construction found only in Mag- 
nesium-Copper Sulphide Units is your 
VISIBLE guarantee against needless 
multiplicity and complications. 

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able ammeter and voltmeter shall be 
provided in the electrical circuit to 
show the arc current and voltage. 

Recommendations Applying Only to the 
Mirror Type Lamphouse 

CAPACITY (Basic): 

I he lamphouse shall be designed to 
be convertiole to accept either ll mm. 
or 15 mm. carbons. 


(Basic) : 

The ventilation of the lamphouse 
shall be so designed that the lamp- 
house will be able to handle as high as 
150 amperes without detrimental heat- 
ing, this to be accomplished with mini- 
mum draft at the carbon arc so as not 
to impair the arc steadiness. (See 
f\ote, "Flicker.") 


Interchangeable mirrors with speeds 
capable of tilling F2.0 and F1.6 pro- 
jection lenses shall be provided.* 


The mirror shall be provided with 
universal adjustments so constructed as 
to maintain their settings. 

SCREEN (Basic): 

An optical system should be de- 
veloped to provide a more uniform dis- 
tribution of light on the screen than is 
now obtained from mirror type lamps. 
(See "Capacity of the Feeding Me- 

Recommendations Applying Only to the 
Condenser-Type Lamphouse 

CAPACITY (Basic): 

The lamphouse shall be designed 
and constructed to accommodate 13.6, 
16, and 18 mm. carbons, and to accom- 
modate in the case of the relay set up, 
condensers capable of filling an F1.6 
lens and cover the camera apertures 
as specified under "The Film Gate and 
Projector Head." 


The condenser lamphouse shall be 
so designed that it will be adaptable to 
a relay condenser system at such time 
as this system may be desirable. 

(Auxiliary) : In the opinion of the Com- 
mittee, the basic recommendation on 
"Adaptability" will probably call for greater 
latitude in positioning and adjusting of con- 
densers, and it has been suggested that the 
front end of the lamphouse be so con- 
structed that it will be adjustable to accept 
different types of optical systems as well 
as those existing at present and those ex- 
pected to be developed in the future. One 
method suggested has been the use of an 
adapter plate or series of rings on the front 
of the lamphouse which will allow, at the 
present time, a stepping down of the size 
of the opening in the front of the lamp- 
house to present systems, and the addition 
of faster systems, at a later date, merely 
by removing the adapter plates or rings. 



The lamphouse shall be so designed 

*NOTE: Present mirror reflectors do not 
produce adequate results in an F2.0 or F1.6 
system and efforts to improve this condition 
should be made. 

that sufficient ventilation will be pro- 
vided for the use of currents as high 
as 250 amperes without detrimental 
heating, this to be accomplished with 
minimum draft at the carbon arc so 
as not to impair the arc steadiness. 
(See Note, "Flicker.") 

Feeding Mechanism and Accessories 
(Applying to Both Type Lamphouses) 


The carbon feeding mechanism shall 
be designed so that the light projected 
on the screen is not subject to periodic 
changes of level attributable to the 
feeding mechanism (see "Light Varia- 
tion") and must be capable of han- 
dling the carbon sizes specified under 


Feed and contact brushes for the 
positive carbon shall be so designed 
and made that the crater, during opera- 
tion, will not change its focal position 
by more than ±0.025". The positive 
head shall be designed so that the posi- 
tive carbon axis at the crater will rotate 
within a circle of a radius of 0.010". 


(Basic) : 

The feeding mechanism shall be so 


FS Condensers are ground and 
highly polished to precision accur- 
acy in curvature and focus. They 
will not discolor. 

Available in extra-heat-resisting 
Pyrex Brand glass and also in reg- 
ular glass. 

FS Reflectors are accurately 
made for correct focus, individu- 
ally tested before shipment, and 
protected by a heat-resisting re- 
fractory backing that is non-peel- 
ing. All FS quality optical goods 
are, of course, guaranteed to give 
satisfactory performance. 

Reconditioning Service 

See your dealer about the FS 
service on resilvering and repolish- 
ing reflectors and condensers. 


266 East 43rd Street, New York 




designed that the negative carbon will 
burn at an angle, in relation to the 
axis of the positive carbon, to obtain 
oplimum efficiency. With present 
equipment and carbons this angle is 
approximately 53°. 


(Basic) : 

An automatic control for the proper 
motor feed shall be provided to keep 
the crater in its correct burning posi- 
tion. Electrical feeds shall be provided 
for both carbons of sufficient latitude 
and control that the carbons may be 
motor-driven under all burning con- 
ditions after having once been set in 
the burning position, this to be accom- 
plished by the use of separate inde- 
pendent motors for the automatic drive 
of both carbons, with alternate control 
for both positive and negative to per- 
mit hand feeding, both backward and 
forward, when desired. 

(Auxiliary) : It has been suggested that 
the automatic control for keeping the posi- 
tive carbon in a correct relative position 
(basic recommendation above) be met by 
the use of a thermostatic or photo-electric 
cell control on the motor feed, either con- 
trol to be actuated by a beam of light from 
the crater of the arc. 

MENT (Basic): 

The negative feed mechanism shall 
be provided with a readily accessible 
adjustment to move it both vertically 
and transversely in relation to the axis 
of the positive carbon. 

(Accessory) : Consideration should be 

given to the possibilities for providing a 

visual target to show the negative carbon 

burning position along the longitudinal axis 



(Continued from page 15) 

as to size and location. At least one should 
be of the conventional stairway type, having 
a. suitable landing at the top or should open 
directly onto a corridor. 

(d) Two openings for each motion pic- 
ture projector shall be provided; one for 
the projectionist's view {observation port) 
shall be not larger than 200 square inches, 
and the other through which the picture is 
projected {projection port) shall be not 
larger than 120 square inches. 

(e) Each opening shall be provided with 
an approved gravity shutter set into guides 
not less than one inch at sides and bottom, 
and overlapping the top of the opening by 
not less than one inch when closed. Shut- 
ters shall be of not less than 10-gauge iron 
or its equivalent, or of Vi-inch hard asbestos 
board. Guides shall be of not less than 10- 
gauge iron or its equivalent. Shutters shall 
be suspended, arranged and inter-connected 
so that all openings will close upon the 
operating of some suitable fusible or me- 
chanical releasing device, designed to oper- 
ate automatically in case of fire or other 
contingency requiring the immediate and 
complete isolation of the contents of the 
enclosure from other portions of the build- 
ing. Each shutter shall have a fusible link 
above it, and there shall also be one located 
over each upper projector magazine which, 
upon operating, will close all the shutters. 

Read These Reasons — 

Tops the Field Because — 



It Offers 

Better screen illumination regardless of make, size and type — Minimum cost 
in current and carbons: MORE LIGHT PER AMPERE! — Maintenance is 
negligible — Every lamp guaranteed mechanically for one year — Has every 
known proved improvement — Modern and simple to operate — Costs no more 
than lamps of inferior quality — Guaranteed by the oldest and largest manu- 
facturer of projection lamps — Practical for either the 500-seat or 5,000-seat 

At Independent Theatre Supply Dealers Everywhere 
In Canada: Dominion Sound Equipments, Ltd., Montreal, Quebec 


47-31 Thirty-Fifth St. 

Long Island City, N. Y. 

There shall also be provided suitable means 
for manually closing all shutters simultane- 
ously from any projector head and from a 
point within the projection room near each 
exit door. 

(f) All shelves, furniture and fixtures 
within the enclosure shall be constructed of 
incombustible material. Tables shall con- 
form to paragraph 117. 

Arc Lamp Ventilation 

(g) Ventilation shall be provided by one 
or more mechanical exhaust systems which 

shall draw air from each arc lamp housing 
and from one or more points near the ceiling. 
Systems shall exhaust to outdoors either di- 
rectly or through a non-combustible flue 
used for no other purpose. Exhaust capacity 
shall not be less than 15 nor more than 50 
cubic feet per minute for each arc lamp plus 
200 cubic feet per minute for the room itself. 
Systems shall be controlled from within the 
enclosure and have pilot lights to indicate 
operation. The exhaust system serving the 
projection room may be extended to cover 
rooms associated therewith such as rewind 
rooms. No dampers shall be installed in 

MAY 1939 


such exhaust systems. Ventilation of these 
rooms shall not be connected in any way 
with ventilating or air conditioning systems 
serving other portions of the building. 

(h) Exhaust ducts shall be of non-com- 
bustible material, and shall either be kept 
one inch from combustible material or 
covered with V-2 inch of non-combustible heat 
insulating material. 

( i ) Fresh air intakes other than those 
direct to the open air shall be protected by 
approved fire shutters arranged to operate 
automatically with the port shutters. 

( i ) Provision shall be made so that the 
auditorium lights can be turned on from 

When other types of current 
conversion cry "Quits" and 
give up . . . 


keeps on round after round 
(year after year) in maintain- 
ing uniformly fine service, 

Ask about the many other 

fine features of the 


Consult the nearest office of The 
National Theatre Supply Co.; in 
Canada, General Theatre Supply 
Co.; or write us 


12692 Elm wood Avenue 
Cleveland, Ohio, U. S. A. 

Exclusive Manufacturers 
of the Transverter 

inside the projection room and from at least 
one other convenient point in the building. 

[Note. — Automatic sprinklers in projection 
rooms have been very successful in controlling' 
fires and reducing losses, and their installation 
is recommended wherever practicable.] 

193. Processing of Film. The processing 
of film, as cleaning, polishing, buffing and 
oiher special treatments, shall not be one 
in rooms where other operations are per- 
formed, except that in motion picture thea- 
tres, cleaning of film may be done in the 
rewind room. 



Section 21. — Motion Picture Theatres 

and Other Occupancies In which the 

Principal Use of Film Is in Motion 

Picture Projection 

211. Enclosure for Projectors. Motion 
Picture Projectors shall be installed in an 
enclosure in accordance with subsection 191. 

212. Rewinding, fa) Rewinding of films 
shall be performed either in a special re- 
wind room at an approved location, or in 
the projection room. If done in the pro- 
jection room, approved enclosed-type re- 
ivind machines should be used. An ap- 
proved can for scrap film having a self- 
enclosing hinged cover shall be provided. 

(b) Rewind rooms shall be at least 80 
square feet in area, with walls and doors 
in accordance with the requirements of sub- 
section 112 and with ceiling of equivalent 
fire resistance, and shall have a vent to the 
outside of the building of not less than 27 
square inches. See paragraph 191 (g) . 
Exhaust ducts shall comply with paragraph 
191 (h) . Shelves, furniture and fixtures shall 
comply with paragraph 191 (/) . 

213 (a). Change word "booth" to "room." 
(1) Omit words "booth or". 

(3) Omit words "or room". 

(4) Change word "booth" to "room." 

214. No collodion, amyl acetate or other 
similar flammable cement or liquid in quan- 
tities greater than 1 pint shall be kept in 
the projection booth or room or rewinding 

215. Splices in film shall be made on me- 
chanical cutting and splicing machines. 
See paragraph 212 (a) on handling of scrap 

217. Operation. Motion picture projec- 
tors shall be operated by and be in charge 
of qualified projectionists, who shall not be 

218. Procedure in Case of Fire. In the 
event of film fire in a projector or else- 
where in a projection or rewind room, the 
projectionist should immediately shut down 
the projection machine and arc lamps, oper- 
ate the shutter release at the nearest point 
to him, turn on the auditorium lights, leave 
the projection room, and notify the manager 
of the theatre or building. 


[Continued from page 11) 

why we are very careful to prevent moist- 
ure and air from getting to it. 

Mr. Finn: What is meant by "a useful 
life of five years"? 

Mr. Kotterman: The life under opera- 
tion conditions, depending upon the use of 
the equipment. It might be perfectly all 
right at the end of five years. We have 
rectifiers delivering much smaller outputs 
than the carbon-arc rectifier demands which 
have been in service ten years. 

Mr. Finn: The General Electric Co. 
ran some accelerated life-tests on the cop- 
per-oxide type of rectifier equivalent to ten 
or eleven years of continuous service. 

The phrase "useful life of five years" 
does not seem right. If General Electric 
ran those for ten years, exposed to all 
sorts of weather conditions, I do not see 
why this particular rectifier should be 
limited to a useful life of five years, pro- 

how much $ 1 can do 

Help us tell the public that 


But treatments must be started in time 

Large gifts are needed by the New York 
City Cancer Committee. But if you can 
spare only $1, bring it today or mail it to 
the Red Door, 130 East 66th Street, N. Y. 
You will receive: 

1. A year's subscription to the Commit- 
tee's new publication of information about 
cancer research and treatment, "The Quar- 
terly Review." 

2. A supply of labels for your packages. 

The remainder of your $1 will be spent 
for the information service, distribution of 
free pamphlets, lectures, exhibits, pub- 
licity, etc. 

// not a resident of New York City, write for 
information to the American Society for the 
Control of Cancer, 1250 Sixth Ave., New York 



vided the safety factor remains constant. 
I know that some railroad rectifiers have 
been running ten years. 

Mr. Kotterman: We have been mak- 
ing this heavy-current type of construction 
only about two years, and the only thing 
we could do was to have an accelerated 
life-test, which we think is equivalent to 
five years. We stopped it at the end of 
that period in order to study the rectifying 
junctions. We have started another life- 
test that we may run an equivalent of ten 

Mr. Finn: We are not dealing with 
high amperages, only 50 or 60 amperes. 

Mr. Kotterman: I think that is a 
rather high current. It means that the 
copper-sulfide rectifier is operating at a 
current-density of 38 amperes per square- 

I might qualify the term "useful life." 
One buys an automobile and expects a 
useful operating life of three years. It 
may continue to operate after that, but 
might not be quite as useful as it w" 
during the first three years. Conceivably 
this rectifier may still operate at the end 
of five years and still be useful ; or the 
voltage output may fall off to the extent 
where it is no longer giving useful service 
for the projection arc. 

Dr. Carver: What happens when the 
rectifier does go bad? Does it go bad sud 
denly, or does it give warning? 

Mr. Kotterman: It gives warning. The 
output begins to fall off. 

Mr. Roberts: What is the voltage drop 
through the rectifier unit on an arc ap- 
plication? What is the efficiency of the 

Mr. Kotterman: The rectifving effi- 
ciency of this type of copper-sulfide recti- 
fier is 50 to 55 per cent. Depending upon 
the circuit conditions, the overall efficiencv 
of the transformer-rectifier combination 
v/ould be lower than the rectifying effi- 
ciency alone. 

Mr. Roberts: What is the drop through 
the unit? 

Mr. Kotterman: One-half volt per 

Mr. Crabtree: What is that in com- 
parison with the copper-oxide rectifier? 

Mr. Elderkin: The copper-oxide recti- 
fier gradually ages. The output drops from 
the time it is new until you can not use 
it anv longer. The resistance increases 
steadily; sometimes it will be so high as 
to cause overheating. This rectifier does 
not do that. It does not age. The effi- 
ciencv is the same throughout a longer 
r"riod of life. The copper-oxide rectifier 
will show a little higher efficiency at the 
c tart, and lower efficiency when it is nldf- 
The averapv efficiencv over a given length 
of time will about be the same for the 

Mr. Crabtrf.e: What is the ratio of in- 
put to output? 

Mr. Elderkin: That depends imon the 
(Continued on next page) 


RCA has signed sound system servicing 
contracts covering 67 theatres of both 
Saenger Amus. Co. and United Theatre 
groups, extending through five states. 


At least 6, and possibly 7, Technicolor 
features will be made by Fox-20th Century 
on its 1939-40 program, the largest single 
season's color group ever to be made by a 
major company. Technical is aiming at a 
grand total of 50 features for next year. 







How Man 


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Enter my subscription for 

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50c per 




MAY 193 9 


circuit, the output, and the number of 
units used. In this particular application 
the efficiency will start at 60 to 65 per 
cent; with the copper-oxide it will drop 
to 40 or 45 per cent. 

Chief Advantage of Unit 

Mr. Kotterman: In our opinion, the 
chief advantage of the copper-sulfide recti- 
fier over the copper-oxide rectifier is its 
tremendous reserve capacity and the fact 
that it operates at an exceedingly high 
temperature without causing destruction of 
the rectifier elements. Also, that we can 
build a rectitying device that will deliver 
the amperage associated with the carbon 
arc in a very small assembly. 

One form of copper-sulfide rectifier meas- 
ures 16 inches in diameter and 12 inches 
in height, weighs 100 pounds, and delivers 
10 kw. of direct current. Of course, those 
figures do not include the transformer. I 
do not think there is any type of contact 
rectifier or other type of d. c. generator 
equipment that can deliver 10 kw. in so 
small a compass as that. 

Mr. Thomas: What are the character- 
istics of this equipment on 25-cycle cur- 
rent, and what happens to the d. c. out- 
put in relation to an a. c. input voltage 

Mr. Kotterman: Laboratory measure- 
ments have shown very little difference 
between the overall efficiency at 25 cycles 
and at 60 cycles. Much larger transformers 
are required to operate on 25 cycles than 
on 60, but the results are practically iden- 

Comparative Portability 

Mr. Strickler: We use from 50 to 100 
of the tungar outfits for portable projec- 
tion, travelling all over the country and 
encountering all kinds of conditions. The 
weight and size are very important. We 
have small arc lights using about 25 am- 
peres. Would your rectifier be less in 
weight or in bulk than similar contact out- 
fits? Single-phase supply is what we meet 
in almost all cases. 

Mr. Kotterman: For single-phase opera- 
tion I doubt that there would be much ad- 


These films have been prepared under the supervision of the Projection 
Practice Committee of the Society of Motion Picture Engineers, and are 
designed to be used in theaters, review rooms, exchanges, laboratories, 
factories, and the like for testing the performance of projectors. 

Only complete reels, as described below, are available (no short sections 
or single frequencies). The prices given include shipping charges to all 
points within the United States; shipping charges to other countries are 

C 7Z>^> 

35- Mm. Visual Film 

Approximately 500 feet long, consisting of special targets with the aid 
of which travel-ghost, marginal and radial lens aberrations, definition, 
picture jump, and film weave may be detected and corrected. 

Price §37.50 each. 

16 -Mm. Sound-Film 

Approximately 400 feet long, consisting of recordings of several speak- 
ing voices, piano, and orchestra; buzz-track; fixed frequencies for focus- 
ing sound optical system; fixed frequencies at constant level, for de- 
termining reproducer characteristics, frequency range, flutter, sound- 
track adjustment, 60- or 96-cycle modulation, etc. 

The recorded frequency range of the voice and music extends to, 6000 
cps.; the constant-amplitude frequencies are in 11 steps from 50 cps. to 
6000 cps. 

Price $25.00 each. 

16-Mm. Visual Film 

An optical reduction of the 35-mm. visual test-film, identical as to 
contents and approximately 400 feet long. 
Price S25.00 each. 

Address I 


Hotel Pennsylvania New York, N. Y. 

vantage as to size or weight over the tun- 
gar equipment. However, for polyphase 
operation there would be. 

Mr. Strickler: We are not so much 
interested in efficiency because we are 
in operation only for an hour or so at one 
time; but when a man has to set up a 
complete outfit in ten or fifteen minutes, 
equipment weighing 500 pounds in cases, 
put on a show in a room similar to this, 
tear down the equipment and put it into 
cases; and then put on another show in 
the afternoon of the same day several 
miles away, we have to consider size and 
weight. Our present units are stripped 
down to about 50 pounds per case. Would 
such capacity be possible with your outfit 
of similar size and weight? 

Mr. Elderkin: The rectifier units re- 
quired, according to the voltage, would ob 
viously be heavier than the equivalent num- 
ber of tubes. Otherwise, the weight of 
the transformer, etc., would be the same. 
The bulk would be greater. 

Mr. Thomas: Does the reserve of the 
rectifier compensate for a. c. line fluctua- 

Mr. Kotterman: No; that is a matter 
of transformer design. With sufficient re- 
actance in the transformer you will main- 
tain reasonably constant d. c. output under 
wide variations of a. c. voltage. A 10- 
volt variation in a 220-volt line might 
cause a variation of only 0.5 to 1 volt in 
d. c. output. Some very recent develop- 
ments using highly reactive transformers 
are better than that. 

Mr. Thomas: What happens when we 
strike the arc? Does the voltage jump, 
and then return to the proper value for 
operating the arc? 

Mr. Kotterman: To answer your ques- 
tion completely and accurately it would be 
necessary to put an oscillograph on the 
outnut of the rectifier. 

However, I have measured the current at 
the instant of striking the arc, and have 
found it to be of the order of 200 am- 
peres. However, that only lasts but a 
fraction of a second, and immediately the 
carbons are separated the current and volt- 
age return to normal. 

Possibility of Overheating 

Mr. Fiferlik: Is the rectifier likely to 
heat up if connected when the arc is no! 

Mr. Kotterman: The rectifier for the 
projection arc or any other heavy-current 
application can withstand normal line-volt- 
age input without suffering damage in any 
way. The leakage current of the copper- 
sulfide rectifier is much higher, of course, 
than that of the copper-oxide rectifier, but 
is not high enough to result in any danger- 
ous temperature. 

Mr. Dash: With regard to "useful life," 
I should like to mention that there are 
motor-generator sets in operation in theatre 
service that have had 20 years of useful 
service, and are still operating well. The 
presence of rotating parts does not limil 
the life of equipment if the equipment . 
well designed. 

Mr. Cuthbert: Is there any disadvan- 
tage in breaking the d. c. circuit instead 
of breaking, as you normally do, the a. c. 
rectifier circuit? 

Mr. Kotterman : It is more desirable, 
of course, to break the a. c. circuit be- 
cause it is more sensitive to excess volt- 
age than other types of contact rectifiers. 
But as I have said, we endeavor to engi- 
neer into each rectifier application the cor- 
rect electrical characteristics so that if you 
do break the d. c. side or operate it under 
the other circuit conditions, it will stand 
such operation without harmful results. 



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The combination Sound-Vision 

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method of changeover is EXCLUS- 
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Patent No. 1,796.970. These com- 
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are priced at $125 per pair, includ- 
ing foot-switches. 

• • • 

Strong ZIPPER Changeovers are 
especially designed and fitted for 
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• • • 

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• • • 



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Get spare photocells for 
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Visitron cells are available for every type of sound projec- 
tion equipment. Theatre supply dealers can advise the 
correct cell for your equipment. Buy from your supply 
dealer. If you wish to have your old cells tested without 
charge, write to G-M Laboratories, Inc., for instructions for 
shipping. Information furnished promptly. 

Here's an important fact to remember — Hollywood 
is now producing finer sound than ever before — be- 
cause movie fans demand good sound. To properly 
reproduce it — and build up your business — install 

New RCA Photophone Magic Voice of the Screen 

• it, ci i •!• i aii¥* f r\ • — available at low cost to 

with Rotary Stabilizer plus Shock-Proof Drive theatres of every size! 

Let's look at facts. You can 
J show the finest pictures in the 
world — but you'll have empty 
seats in your theatre if the sound 
is poor. Because nowadays movie 
fans know good sound from bad — 
and patronize the theatre where 
listening is as much fun as looking. 
Hollywood knows this and 
that's why Hollywood puts such 
excellent sound on its films. But 
how about you — are you letting 

an outmoded sound system hurt 
your takes? 

It will pay you to find out about 
the new RCA Photophone Magic 
Voice of the Screen. For here's the 
equipment built for true reproduc- 
tion of modern movie sound. It's 
the tonic your box office needs. 
And its low cost will surprise you, 
just as its many new features will 
delight you. Full details from your 
RCA Photophone representative. 

RCA Photophone's service organization has a low cost theatre service plan in which you'll be interested 

Only the New Magic Voice 
of the Screen offers 
all these Features! 

This splendid new equipment gives you full 
assurance of constant film speed by adding 
the amazing new Shock-Proof Drive to the 
famous Rotary Stabilizer! Besides this great 
feature, the new Magic Voice brings you 
new styling, new protection, new conve- 
nience, new added reserve power and many 
other outstanding proofs that it's the best 
value you've ever seen! Ask your RCA 
Photophone representative for complete 

Better sound means better box office 
and RCA tubes mean better sound. 

JULY, 1939 




It is time to be making plans for your summer 
renovizing program. Your problem is how to 
spend the funds available so as to give your 
theater the greatest possible increase in draw- 
ing power. 


If not, you should give it careful consideration 
in your plans, for more than a third of the 
theaters in this country are now using this 


superior, snow white, projection light. 

The little book illustrated above, "The Eternal 
Triangle in Picture Projection," tells you in 
clear, simple language, supplemented by explan- 
atory illustrations, how Simplified High Inten- 
sity projection attracts new patronage to your 

^Wndte jjOSi a friee, ootuf, today! 








The words "Nationd" and "Suprex" are trade-marks of Nalinnal Carbon Company, Inc. 


Unit of Union Carbide IHM and Carbon Corporation 


General Offices: 30 East 42nd Street, New York, N. Y. 


JUL 25 1939 


Edited by James J. Finn 

Volume 14 

JULY 1939 

Number 6 

Index and Monthly Chat 5 

Supplementary Aids to Servic- 
ing Sound Reproducing Sys- 
tems 7 

Leroy Chadbourne 

Panoramic Projection Equip- 
ment 13 

A. Gillett, H. Chretien and 
J. Tedesco 

Film-Weld Endorsed by LP. . . 14 

Fundamentals of Mathematics, II 15 
George Logan 

Process Projection Specifica- 
tions, II 18 

Report by Academy of 
M. P. Arts and Sciences 

Defining Light-Sensitive Cells 19 
Samuel Wein 

The Baird Theatre Television 

Receiver 21 

Matt Raymond, jr. 

New Academy Theatre lest 
Reels 22 

News Notes 

Technical Hints 

Miscellaneous Items 

Published Monthly by 



Circulation Manager, Ruth Entracht 

Subscription Representatives 

Australia: McGills, 183 Elizabeth St., Melbourne 
New Zealand: Te Aro Book Depot, Ltd., 64 Courtenay Place Wellington 
England and Dominions: fm. Dawson & Sons, Ltd., Pilgrim St., London, E. C. 4. 

Yearly Subscription : United 
States and possessions, $2 (two 
years, $3) ; Canada and foreign 
countries, $2.50. Single copies, 
25 cents. Changes of address 
should be submitted two weeks 
in advance of publication date to 
insure receipt of current issue. 
Entered as second-class matter 

February 8, 1932, at the Post 
Office at New York, N. Y. under 
the act of March 3, 1879. 
Contents copyrighted 1939 by 
James J. Finn Publishing Corp. 
International Projectionist 
is not responsible for personal 
opinions appearing in signed 
articles in its columns. 

Monthly Chat 

REPEATED requests from projection- 
ists for information relative to the 
new series of Bausch & Lomb //2.0 pro- 
jection lenses induce this corner to pass 
along the statement of the manufacturer 
that details anent this new series will 
not be forthcoming until late Summer 
or early Fall. We'd like it to be other- 
wise, but we can hardly break into the 
B. & L. plant and seize the data. 

• • • 

Elsewhere herein is a summary of 
theatre television development as spon- 
sored by the Baird people in Eng- 
land. This summary should serve to 
soothe the frayed nerves of some of the 
more jittery projection men, particularly 
those who have been reading in other 
journals about current telecast images 
"approximating" the quality of feature 
film releases of "a few years ago." 

• • • 

Several responses to the suggestion 
that the P. A. C. be revived have been 
received; but this corner detects no 
flowering of unrestrained enthusiasm 
anent the idea among the craft at large. 

• • • 

We've cleared our throat preparatory 
to shouting "I told you so" with respect 
to the campaign by the distinguished 
Mr. F. H. Richardson in favor of ship- 
ping "tails out" prints to theatres. Our 
scouts report that the exchanges, as 
forecast herein, have taken advantage 
of this practice to give prints even less 
inspection than heretofore — which adds 
up to a figure approximating zero. 
"F.H.," fortunately for him, doesn't have 
to run such prints. 

• • • 

Two significant items culled from the 
industry news: 610 projectors are in 
use in Chicago schools. 590 shorts with 
sound accompaniment have been made 
available by the M.P.P.D.A. for school 
use. Now, if somebody would compile 
a list of other non-theatrical showings 
for which admission is charged, and also 
ascertain the source of product for these 
itinerant exhibitors, movie theatres 
might be better able to cope with this 
growing problem. 

• • e 

No httle confusion exists among pro- 
jectionists relative to jproperly classify- 
ing the many and varied types of sound 
track now in general use. An attempt 
to settle the dust hovering over this 
question will be assayed by I. P. if ever 
a certain Mr. Kelly of Hollywood can 
be dragged back from Malibu and put 
to work. 

• • • 

No reader has yet threatened to shoot 
us for sponsoring the current series of 
articles on mathematics by the capable 
Mr. George Logan of the M-G-M stu- 
dios, thus we hazard the guess that he's 
putting over his stuff. 

We've essayed this task of 'selling' 
math on two previous occasions, with 
results that we elect to forget about. Any 
comment on the current series? 

JULY, 1 » 3 » 




Section A-9437, 

Appliance and Merchandise Department, 

General Electric Company, Bridgeport, Conn. 

Please send me the folder which tells all 
about G-E Copper Oxide Rectifiers for Motion 
Picture Projection Service. 

And don't forget — when you see the 
General Electric monogram on a copper 
oxide rectifier, you can rest assured that 
it was designed RIGHT. It was built 
RIGHT. And tomorrow doesn't find 
it obsolete! 










JULY 1939 

Supplementary Aids to Servicing 
Sound Reproducing Systems 

WHEN all other sources of sound 
system data have been exhausted 
(see I. P. for March, 1939, p. 
12; and April, 1939, p. 7) the physical 
apparatus can be inspected and its wir- 
ing traced, schematic and other dia- 
grams then being drawn accordingly. 
This is not an easy job; it is difficult, 
tricky, and takes time. It should never 
liave to be done in the projection room. 
However, there are three sets of cir- 
cumstances that may make this work 
necessary, even indispensable. 

First and most serious is when pro- 
vision of proper drawings has been de- 
layed until after the arrival of trouble 
of such nature that it can't be fixed 
without the aid of drawings. The only 
consolation here is that the necessary 
diagrammatic information can usually 
be restricted to one very small area of 
the system, where the trouble has pre- 
viously been isolated by suitable tests 
made at marked connection points. 
Small or large, however, simple or 
complicated, the faulty part of the 
system often has to be drawn out on 


paper before the circuit arrangements 
can be understood and the trouble diag- 
nosed accordingly. 

It goes without saying that the draw- 
ing of diagrams delays trouble-shooting, 
and should not be left until after 
trouble appears. There are conse- 
quently two other occasions, which do 
not involve immediate trouble, when 
drawings may have to be made to 
assure their availability when needed. 

The most common of these is where 
there is doubt as to the accuracy of 
such drawings as are available. Changes 
may have been made after the equip- 
ment was installed and not properly 
recorded on the diagrams. This often 
happens, and when it does the drawings 
are worse than useless: they not only 
i'ail to lead the trouble-shooter down 
the right path but misdirect him into 
a dead end. The same result ensues 

when original data have been damaged, 
worn out or mislaid, and new ones, 
obtained from the manufacturer, show 
subsequent modifications and improve- 
ments that the apparatus installed 
doesn't have. Physically checking the 
wiring, in advance of trouble, is the 
only real remedy. 

Finally, there are theatres that can- 
not obtain drawings, either because the 
manufacturer has gone out of business 
cr because he has changed models and 
no longer has spare diagrams of the 
old ones, or (as still is unfortunately 
the case) he refuses to supply drawings. 

Any of the aforementioned circum- 
stances puts an unpleasant but un- 
avoidable job squarely up to the pro- 
jectionist. The job is not without its 
compensations: he who handles it is 
hkely to know the circuits of the sys- 
tem from then on. 

Most theatres buy sound service; 
still, system data should be in the pro- 
jection room. If it is not, the projec- 
tionist can do little or nothing except 
wait for the service man — which means 

JULY, 1939 

that meanwhile the theatre is out of 
luck. With diagrams, the projection- 
ist, even if he doesn't find the trouble, 
can at least eliminate false leads and 
save the serviceman that much time. 
Further, absence of data makes break- 
down more likely: the projectionist can 
hardly be expected to put a correct 
interpretation on symptoms of coming 
trouble or to take needed precautions, 
if the circuits are a mystery. 

• Types of Drawings 

Drawings that may have to be made 
in a projection room can be divided 
into the two categories of external and 
internal circuits. Fig. 1 represents the 
external circuits of a portion of a 
modern sound system. Fig. 2 shows 
the circuits of a modern amplifier (not 
part of the system shown in Fig. 1). 

External circuits are the easier to trace. 
In time of trouble they are fully as 
important as internal circuits, perhaps 
more so, since it is often necessary to 
apply tests to Fig. 1 in order to isolate 
trouble to the interior of some such 
panel or cabinet as Fig. 2. At the 
same time, Fig. 1 naturally can give 
trouble on its own account. 

Circuits corresponding to Fig. 1 are 
usually easy to obtain. All manufac- 
turers now supply them with new equip- 
ment as a guide in doing the pre- 
liminary work of installation. Not all 
are as complete as Fig. 1; some do 
not show the terminals to which each 
individual wire connects. All are valu- 
able, however, should be kept after in- 
stallation is completed, and modified to 
make them complete if necessary. Cor- 
responding drawings of older systems 

may not be available; if obtained on 
request, they may not represent the true 
situation, and should always be 

• Safe and Unsafe Testers 

Amplifier schematics of the type of 
Fig. 2 cannot always be obtained even 
for new systems, and are not always 
accurate. Some types of amplifiers, 
having proved satisfactory, are supplied 
by the same manufacturer over a period 
of years, usually with slight changes 
from time to time. There may be a 
series of such amplifiers (or other 
units) all pretty much alike but dif- 
ferent enough to produce great con- 
fusion when trouble is traced through 
one with the help of a diagram that 
applies to another. Drawings not ship- 
ped with the equipment at the time 
of original installation are always under 





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suspicion and should always be checked. 

In drawing a diagram from actual 
apparatus a satisfactory circuit tester 
is the most important appliance needed, 
aside from paper and pencil. Bell and 
buzzer are not satisfactory testers for 
any kind of sound work. Neither is a 
trouble lamp. The smallest size %-volt 
flashlight bulb and corresponding bat- 
tery are reasonably safe if not used on 
photocell coupling transformers. Head- 
phones and battery are almost always 
safe to use. Aside from partial or 
complete undesirability, however, none 
of these testers gives full information, 
and relying on them needlessly compli- 
cates the work. 

Those of the aforementioned testers 
that permit the passage of more than 
a few mils of current (buzzer and bat- 
tery, etc.), may permanently magnetize 
the core of a coupling transformer. As 
everyone knows, a bell-ringing trans- 
former, for example, will not couple 
sound circuits satisfactorily. It is de- 
signed for 50 or 60 cycles, losing effi- 
ciency at other frequencies; while a 
good sound transformer must be equally 
efficient from 40 to 10,000 cycles. The 
type of metal used for core, and its 
degree of magnetization, is very impor- 
tant in this connection. Saturating the 
core by passing through the windings 
currents much stronger than they were 
ever intended to carry may result m 
permanent damage to sound quality, 
and very difficult to run down in a 
projection room. 

Crude testers of this type also give 
insufficient information. A high-resist- 
ance circuit, such as the 100,000-ohm 
input of Fig. 2, is likely to show up 
as an open circuit with such devices. 
A low resistance, such as the 33-ohm 
meter resistor in the plate line of the 
first tube of Fig. 2, is likely to show 
up merely as a connecting wire. This 
does not mean that the headphones or 
very small flashlight bulb cannot be 
used, if nothing better is available, but 
they complicate the job needlessly. 

The ohm-meter, or as second choice 
a battery and high-resistance voltmeter, 
are always to be preferred. 

Further, a soldering iron is needed. 
Refer to Fig. 1. The "Com" terminal 
of the right-hand volume control am- 
plifier (about the center of the draw- 
ing) carries three wires which go to 
different points. One of them touches 
at the "Com" terminal of the left-hand 
volume control amplifier, so that alto- 
gether there are at least four terminal 
studs in this system which are wired 
together. Still other studs may link on 
by reason of internal connections 
through switches or other junctions in- 
side of a panel; for example, the third 
output wire from the top, at the right 

of Fig. 2, is internally united with the 
sixth output wire from the top. 

Where the wires go into a cable 
form, or a conduit, so they cannot be 
seen and traced by sight and hand, such 
linkages make the process of drawing 
a circuit extremely difficult, unless the 
terminal connections are temporarily 
opened with a soldering iron. 

In some cases several connections 
may have to be opened simultaneously, 
to make sure the apparent indications 
are truly accurate. Wherever this is 
the case, every wire must be tagged to 
make sure it goes back at the right 
terminal. No easier method of blow- 
ing out an amplifier has ever been 
invented than trusting to memory in a 
matter of this kind. The tags may be 
mere scraps of paper poked on the 
wire, each having first been carefully 
inscribed with the necessary informa- 
tion. Small "price tags," bits of card- 
board with string attached, can be had 
in any stationery store at 10c a hun- 
dred. They do not tear, and are in 
every way superior. 

A group of tags of any kind should 
never be marked up in advance and 
then put on wires one by one. That 
is how they get on the wrong wires. 
Each one should be marked at the last 
minute before it is attached. The string 
type can, and should, be put on its 
wire before the wire is disconnected 
from its terminal. 

The process of checking an existing 
diagram, such as Fig. 1, is not very 
different from that of making a new 
diagram. Merely checking the wires 
one by one against the drawing in hand 
is likely to lead to error. There is a 
natural tendency to believe that con- 
ditions are as the drawing represents 
them, and oversight becomes easy. It 
is better to make a new drawing which 
is then compared with Fig. 1, using 
that diagram, however, as a guide to 
facilitate the work without relying on 
it completely. 

The same is even more true of Fig. 
2. Consider the left-hand side of the 
choke coil shown above and just right 
of the filament of the rectifier tube. 
Ten different parts (seven resistors and 
three condensers) connect directly to 
the left-hand side of that coil. Possi- 
bilities of confusion are obvious. The 
only safe way is to mark down the 
connections as the ohm-meter shows 
them, and check the diagram afterward 
against the drawing thus made, re- 
checking where discrepancies appear. 

It is helpful of course to use the 
existing diagram as a guide, without 
trusting it very much. But it is futile 
to check the ten connections one by 
one, referring to the diagram each time 
and approving it before going on to the 

next connection. That is trusting mem- 
ory too far. A separate drawing should 
be made. 

In other words, checking a drawing 
and making one are about the same 
process, except that in the former case 
reference to the diagram already at 
hand helps speed the work. 

• Tracing External Circuits 

In tracing arrangements of the type 
of Fig. 1 experienced men generally 
begin by drawing all the terminal 
blocks, with each individual terminal 
post and its designation as shown on 
the physical equipment. Where the 
equipment is not marked, care is taken 
to draw every terminal post in exactly 
its correct position. Where chances of 
confusion are great, by reason, for ex- 
ample, of crowding, a red crayon is 
sometimes used to number the terminal 
points in the actual equipment, corre- 
sponding numbers being set down on 
the paper. Nothing is trusted to 
vnemory — nothing. 

When the terminal posts have all 
been properly drawn and identified, 
the work of tracing wires begins. It 
involves two processes. One is straight 
tracing with the ohm-meter or other 
instrument. The other involves some 
temporary guessing, always confirmed 
by the tester, intended to make the 
work easier. 

With the arrangements of Fig. 1. 
work may begin at any convenient 
point, which might be pec terminal 1 in 
No. 1 soundhead. The jumper to ter- 
minal 2 of that pec connection is obvi- 
ous. The coaxial cable connection to 
Wo. 1 volume control amplifier is also 
obvious. The other four connections 
between No. 1 soundhead and No. 1 
volume control amplifier may also be 
visible, or conduit may be buried in 
the floor and wall, connecting with the 
projector base. If so, the wires may 
go anywhere; the conduit vanishes in 
the floor, but a little guessing, based 
on switching arrangements and general 
probabilities, is in order, and No. 1 
\olume control amplifier will very likely 
be checked first. 

The details of investigation are, how- 
ever, very different when the connec- 
tions are subject to some visible check 
and to instrumental inspection only. 
The easier case, that in which eye and 
hand can supplement the instrument, 
may be considered first. 

Work may begin almost anywhere 
say with No. 1 soundhead. Four wires 
can be seen, running to No. 1 volume 
control amplifier. The markings on the 
terminal board of No. 1 control ampli- 
fier offer some further help. Finally, 
the ohm-meter shows definitely that 
there is a solid connection between No. 

JULY. 1939 

1 exciter terminal in the soundhead 
and No. 1 terminal in the amplifier. 

The only question remaining is: does 
that connection arrive directly from 
the soundhead, or indirectly through 
the other wire also tied to amplifier 
terminal No. 1, or indirectly through 
some other amplifier terminal and the 
amplifier's internal circuits? Tugging 
and observation may help here, but the 
only certain assurance is provided by 
tagging the two wires on No. 1 ter- 
minal and removing them; then testing 
the terminal itself and each wire singly, 
with the ohm-meter. 

The true connection thus found is 
properly added to the new drawing. 
The wires are not replaced imme- 
diately; they are tagged and will not 
go back on the wrong terminal, thus 
avoiding excessive connecting and dis- 

Similar procedure is then followed 
anent the other three wires, until all 
the output connections from soundhead 
No. 1 have been traced and set down 
on paper. The ground connection alone 
is left unchecked; grounds are linked 
in so many ways, not only by wire but 
through conduit and any other metal 
work that may be handy, as to make 
tracing them a difficult business seldom 
undertaken except to run down a 
"ground loop" that is causing line 
frequency hum. Mere addition of the 
ground symbol is sufficient for most 
other purposes. 

Information gained by tracing No. 1 
soundhead connections will aid in in- 
vestigating the other head — but only as 

a guide. A short inspection of Fig. 1 
will show that the two circuits are 
not at all alike in some details. The 
wiring of No. 2 head is traced sepa- 

When conduit runs are concealed, or 
when they link on to other conduits, 
the work becomes much more difficult. 
Consider the line leading from No. 1 
exciter terminal of No. 2 soundhead. 
Careless use of the ohm-meter might 
indicate a direct connection to the d.c. 
terminal of No. 2 volume control am- 
plifier. This is not the case. The dif- 
ference is unimportant with respect to 
current, but may be very important to 
a trouble-shooter looking for a break 
or a short. 

The first job is to find the conduit 
that comes from No. 2 soundhead. This 
may be done by considering pipe sizes, 
counting the number and kind of wires 
in each pipe, and tugging the wires; 
and in very extreme cases by unsolder- 
ing a whole set of wires after they 
have been properly tagged, and then 
pulling back. All of the wires thus 
identified are unsoldered from all ter- 
minals and from each other, and in- 
dividually checked with the ohm-meter. 
If the system has been properly instal- 
led, with no splice in any conduit, there 
is no chance of mistake. As a further 
check, couplings may be opened and 
wires tugged. 

If there are splices inside a conduit, 
which cannot be seen or reached by 
opening couplings, the case may be 
hopeless. Systems so installed have on 
occasion developed troubles that proved 

incurable, yielding only after all wiring 
had been pulled out and reinstalled 
properly. Assuming, however, that the 
equipment was correctly put in, a cor- 
rect drawing can be made of its con- 
nections, even with completely con- 
cealed conduit, provided proper pre- 
cautions are taken. 

As the work proceeds wires that have 
been fully identified, and cannot pos- 
sibly contribute confusion to other cir- 
cuits, may be restored to their proper 
terminals. Thus, in Fig. 1, the input 
circuits to the volume control amplifiers 
can be restored when only the output 
circuits are left to trace. 

Some sound systems are so simple 
that their external connections, includ- 
ing stage wiring, can be traced down 
in an hour or two. Some are so com- 
plex that the work may require several 
nights. When the work is done in ad- 
vance of trouble, it can be done a 
small bit at a time; but of course very 
little of it can be done while a show 
is running. 

• Tracing Internal Circuits 

An internal circuit, similar to Fig. 2, 
is more difficult to trace because of its 
greater complexity, one item of which 
has already been mentioned, but often 
easier to check because wires are likely 
to be color coded. Wires that are 
not bound in cable forms can be traced 
visually and by hand. Wherever there 
is the slightest doubt, the ohm-meter is 
used for confirmation. 

The most convenient procedure gen- 
{Continued on page 25) 


u o 


|| nm ^ 







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The outstanding special features they 
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whole motion picture industry. Eastman 
Kodak Company, Rochester, N. Y. (J. E. 
Brulatour, Inc., Distributors, Fort Lee, 
Chicago, Hollywood.) 



for general studio use for all difficult shots 


for backgrounds and general exterior work 

JULY ,1939 11 

Two Standout Projection Aids 

Practical Projectionists 
Wrote This Ad! 

Balaban & Katz Corporation 

Executive Of-fmoes 

Chicago Theatre Building 

May 13, 1939 

Essannay Elec. Mfg. Co. 
908 South Wabash Avenue 
Chicago, Illinois 


The splendid service rendered by the Strong 
Zipper Changeover prompts the writing of 
this letter. We consider a reliable changeover 
as among the most important projection acces- 
sories; and among all changeovers we have 
concluded that the Strong Zipper tops them all. 

This was forcibly brought home to us during 
the recent showing of "Union Pacific" at this 
theatre. During this performance we were 
continually going from our standard-size pic- 
ture to a "blow-up" of twice our regular screen 
size. The Strong Zipper Changeovers, with 
which we equipped our three Simplex pro- 
jectors more than a year ago, performed per 
fectly and enabled hair-trigger changeovers. 

Not only is the Strong Zipper reliable in 
performance, but it is extremely simple in 
construction and very easy to install. Your 
treadle footswitch, which completes the unit, 
is the best which we as projectionists have 
ever seen or used. 

Having been consistent users of Strong 
changeover devices for the past 17 years, ever 
since the opening of this theatre, we are very- 
glad to attest to the excellence of your 
changeover to the practical projectionist. 

Martin Johnson E. Glenn Sweeney 
Harry Ragan Robert P. Burns 

Seth O. Noble 
Projection Staff, Chicago Theatre, Chicago, Illinois 

For Perfect Changeovers — 


A New and Wholly Different 

Reel End Signal 

that does not touch the film or reel. 

This new device is strictly mechanical and 
requires no batteries, no transformers, no gov- 
ernors, and no presetting by the projectionist. 
It does not touch the film or reel, and it is not 
dependent upon any change in the normal 
smooth operation of the projector. 

One minute before the end of a reel this 
Reel End Signal gives a clear, distinct signal of 
15 seconds duration — then it stops. Simply 
yet sturdily constructed, this Reel End Signal 
has performed its intended function unerringly 
in more than 1000 tests under practical condi- 
tions in various theatre projection rooms. 

Installed in 5 minutes, the Reel End Signal 
has no component to get out of kilter or require 
any adjustment. Orders accepted now for 
delivery July 30 and thereafter. A complete 
description will appear in the next issue of this 

Orders for the Reel End Signal have 
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which approved the device immediately 
upon its first demonstration. 


Makers of Precision Projection Equipment for 25 Years 

908 South Wabash Ave. Chicago, Illinois, U.S.A. 



Panoramic Projection Equipment' 



FROM the very time of its incep- 
tion the cinema art seems to have 
been beset by the rigid limitations 
implied by the use of an almost square 
frame, and the sound-track has only- 
accentuated the inharmonious propor- 
tions of the screen projection. How 
is one to overcome the insurmountable 
limits imposed by the standard size of 
the film? Instead of a screen five to 
six meters wide (1 meter = 3.281 
feet), it is possible to use, for example, 
a screen ten to twelve meters wide, 
but the height of the picture will in- 
crease accordingly, and what we shall 
see will be a more or less monstrous 
enlargement wherein the defects of the 
film, particularly the graininess, will 
appear grossly exaggerated. 

Such attempts to get away from the 
convention system are prompted by a 
desire to be liberated from the limita- 
tions of the exceedingly narrow frame, 
to suit the diverse needs of an art the 
very essence of which is motion and 
space. The technical solution to the 
problem was not actually attained until 
the appearance of the French invention 
of Professor Chretien. 

In discussing this subject, is must be 
pointed out that it is believed that 
projection of such dimensions has never 
before been realized, either in a thea- 
tre or outdoors. One of the largest 
projection screens was built and used 
by Lumiere in 1899 in the Galerie des 
Machines of the Paris Exposition. It 
measured 30 meters wide by 24 meters 
high and required a projection distance 
of 200 meters. This panoramic screen 
had an area of 600 square-meters, 60 
meters long by 10 meters high. The 
largest screen constructed for a theatre 
is that of the Gaumont Palace, which 
has a normal area of 100 square-meters 
and may be enlarged to 200 square- 
meters when certain scenes of the film 
being projected permit a panoramic 

• Screen Requirements 

To obtain sufficient brightness of the 
projected images, it is necessary, on 
the one hand, to use extremely power- 
ful arcs and, above all, to consider the 
problem of the reflective power of the 
screen. After repeated trials the best 
lesults were obtained with a screen 

consisting of a cloth to which were at- 
tached small and perfectly spherical 
glass beads. However, a beaded cloth 
of such dimensions could not be prac- 
ticable for outdoor use. It was there- 
fore necessary to develop a screen cap- 
able of withstanding the weather, and 
it was decided to study the possibility 
of placing the beads on a wall instead 
of on a screen. 

This particular screen consists, first, 
of a support a few centimeters thick, 
consisting of a mixture of lime and 
sand in adequate proportions. When 
dry, this support was covered with sev- 
eral coats of insulating varnish to pre- 
vent any possible reaction of the lime 
and sand support upon the screen 
proper. This coating of varnish was, 
in turn, covered with six successive 
layers of zinc white; and, finally, these 
layers were coated with an adhesive 
varnish onto which the beads were 
thrown by means of a special com- 
pressed-air gun. 

The resulting screen is, of course, 
directional, having its maximum reflec- 
tivity within an angle of approximately 
43 degrees. Outside the 43-degree angle 
the reflective power is reduced about 
one-half. Nevertheless, the screen at 
the Palace of Light, its present posi- 
tion, permits an audience of 4,000 per- 
sons, as a minimum, to enjoy the pro- 
jection under excellent conditions of 
visibility and brightness. 

One of the greatest difficulties was the 
problem of image brightness, and it was 
necessary to take into consideration the 
surrounding light, as adequate darkness 

within a radius of 200 or 300 meters 
around the Palace was entirely out of 
the question. However, the brightness 
of this gigantic image is even better 
than that obtained in many motion 
picture theatres using projection screens 
of average dimensions. 

The screen was installed on the 
facade of the Palace of Light (Fig. 1), 
and was exposed to the weather dur- 
ing the period of the Exposition. The 
facade of the Palace, and the screen 
itself, were slightly concave, which 
helped to avoid the marginal distor- 
tion that would have occurred had the 
facade been flat, since the apparatus 
at the right projected the images on 
the left of the screen, and vice versa. 

In order to project films of standard 
size (18 by 24 mm.) upon this large 
screen, standard, the surface of which 
measures approximately 600 square- 
meters, new methods, in addition to the 
use of a screen of great reflective 
ability, projectors of tremendous power, 
highly luminous optics, and so forth, 
had to be adopted. A special difficulty 
was encountered with respect to the 
shape of the screen, the width of which 
was six times the height, whereas the 
width of the film images barely ex- 
ceeds the height. This difficulty was 
overcome by the use of two connecting 
projectors, each equipped with a special 
optical device known as the "Hyper- 

• The Hyper gonar Lens 

The Hypergonar lens was invented 
in 1927 by Professor Henri Chretien, of 


screen on 
the facade 

of the 

Palace of 



•J. Soc. Mot. Pict. Etag., XXXII (May. 1939). 
**Btockliss-Simplex, Paris, France. 
tUniversity and Optical Institute of Paris, 

tParis, France. 




the University and Optical Institute of 
Paris. It is a sort of optical trans- 
former. It does not produce real pic- 
tures by itself, but if set before an 
ordinary photographic objective doubles 

tion" they likewise lack — the visual ex- 
tension required to produce this effect, 
and, in short, the harmony and supple- 
ness of expression of which the cinema 
had been long deprived — an art which 


of projectors 




the field of the objective in one direc- 
tion only, which in this instance is 

A picture 24 mm. wide may thus be 
registered on a film that would nor- 
mally require a 48-mm. picture. When 
the picture is projected, a similar 
optical device, placed before the pro- 
jector, spreads out the luminous beams 
horizontally, thus restoring the objects 
to their proper shape. The lenses used 
are not of the ordinary spherical 
variety, but are cybndrical, and are 
more difficult to grind to the required 
degree of perfection than ordinary 

The total field required to cover the 
huge screen was obtained by juxta- 
posing two partial fields, each having 
been previously doubled by means of 
the Hypergonar. A special camera-type 
base permitted the automatic connec- 
tion of the two equipments in accord- 
ance with the focal length of the objec- 
tives used and made it possible to drive 
them synchronously by means of an 
electric motor. 

As a result of the combination of 
these methods, it was possible to pro- 
ject upon the largest screen in the 
world, with considerable brightness, pic- 
tures that had been magnified six hun- 
dred times in height and twelve hun- 
dred times in width, or seven million 
times in area; and this was accom- 
plished in spite of the general illumina- 
tion prevailing in the surroundings. 

Natural vision is thus reconstructed 
on the screen in a most remarkable 
manner. Instead of viewing the film 
through a narrow space — a square loop- 
hole — we see it unfolded before us as 
it would be in nature. No doubt many 
cinematographic effects are lost through 
such a panoramic extension, but it is 
no less true, on the other hand, that 
with this device many pictures are re- 
created and endowed with the "aera- 

trom its very nature and scope was 
destined to develop freely and at ease 
after the panorama of nature and life. 

• Other Projection Adjuncts 

The projection proper is provided by 
two standard Simplex projectors with 
rear shutters, which makes it possible 
to use 250 amperes per arc without 
heating the film dangerously. These 
are driven in synchronism by a third 
Simplex apparatus, identical to the 
others, through two universal couplings. 
The third projector carries also a Thomp- 
son sound reproducer (Fig. 2). The cen- 
tral projector is driven by a 1%-hp. 

Each Simplex projector is equipped 
with an "Ultimum" Taylor-Hobson, 
extra-luminous objective, with a fixed 
focus of 120 mm. and an aperture of 
f/2. In addition, each projector is 

equipped with a sliding device for in- 
serting the Hypergonar lens. Each pro- 
jector is also equipped with a Hall & 
Connolly high-intensity lamp. The cur- 
rent in each arc lamp is 250 amperes 
at 70 volts. 

As this projection is in a class by 
itself and requires perfectly homo- 
geneous luminous zones, it was neces- 
sary to use extra-luminous Bausch & 
Lomb condensers to concentrate the 
light of the arc upon the picture gate. 
The arcs are fed by a special 800- 
amp. 110-v. generator, and 16-mm. posi- 
tive and 11-mm. copper-coated negative 
carbons are used. 

To photograph the scenes two 
cameras are necessary, each taking 
simultaneously one-half of the picture. 
Each camera is equipped with a Hyper- 
gonar lens. Each half-image is pro- 
jected simultaneously by the two out- 
side projectors, the right-hand projector 
projecting the image on the left-half 
of the screen, and vice versa. The 
junction of the two images is smoothed 
out by special masks consisting of two 
stationary shutters, the edges of which 
are cut like the teeth of a saw and set 
into the light-beams where the latter 
superimpose. Each of these stationary 
shutters was set about one meter in 
front of each projector, on the left 
and right, outside the beams. The 
shutters could be adjusted by means of 
a micrometer screw, thus concealing 
almost entirely the junction of the two 

Standard film can be projected by 
the central projector, the outside pro- 
jectors merely running idle. The pro- 
jected image in such case measures 14 
x 10 meters, the brightness being about 
the same as in the case of panoramic 
projection. The distance between the 
projectors and the screen was approxi- 
mately 60 meters. Projection occurred 
daily from 9:30 A.M. to midnight, and 
the apparatus operated quite satisfac- 

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flows as freely. 

2. Its rate of evaporation is very 

3. It will not thicken or harden, nor 
does it ever require any thinner. Sam- 
ples left exposed to the air until almost 
completely evaporated exhibited the same 
binding strength as when the container 
was first opened. 

4. It made a very secure patch, even 
by hand, that exhibited greater binding 
qualities than samples of film cement 
tested at the same time. 

5. Because of its nature, it made a 
thinner join than samples of film cement 

6. It is equally efficient on both 
nitrate and acetate film, whether in 
black-and-white or in color. 

Film-Weld is the product of a mid- 
Western university laboratory, and it 
has long been used in the plastics field. 
Discovered by a film laboratory tech- 
nician, its application to the motion 
picture field followed speedily. It is 
distributed exclusively by Larry Strong, 
Inc., 1241 So. Wabash Avenue, Chi- 
cago, 111., who reports that Film-Weld 
has already been adopted as standard 
by numerous theatre circuits, including 
Balaban & Katz; by laboratories, ex- 
changes and studios. Prices compare 
favorably with film cement. 

I. P. considers Film-Weld a highly 
efficient and economical aid to better 
projection and recommends it unquali- 



Fundamentals of Mathematics 



//. Positive and Negative Numbers; Addition, Subtraction, 
Multiplication, and Division of Monomials. 

It will be a help if the reader digest each article as it appears, 
for the ideas presented in subsequent sections hinge upon an under- 
standing of topics discussed in earlier sections. Further, it is desir- 
able that the issues of this series be cached away after reading, as 
back-reference may be. useful before the series is completed. 

The various examples given throughout the series will be best 
understood if the reader will work them out on paper, duplicating, 
step-by-step, the solutions given in the text. 

BEFORE we wade right into our 
discussion of positive and negative 
numbers, a good general idea to 
keep in mind is: if a quantity is under 
consideration, and another quantity in- 
creases the quantity under consideration, 
the second quantity is positive. 

If a quantity is under consideration, 
and another quantity decreases the 
quantity under consideration, the sec- 
ond quantity is negative. 

Certain things should be said about 
the physical meaning of positive and 
negative numbers. Now, insofar as posi- 
tive numbers are concerned, most every 
material thing or phenomena within our 
conception can be counted, measured, 
weighed, timed, or otherwise evaluated 
by the system of positive numbers. But 
this universality of application is not 
true of negative numbers. You cannot 
have a negative number of sheep, for 
example. Nor can you have a negative 
population, a negative weight for a 
piece of iron, or a negative number of 
boats. You either have a positive num- 
ber denoting the magnitude of such 
physical things, or you have none at all 
— that is, zero. 

On the other hand, there are instances 
wherein negative numbers can be and 
are used to manifest a state of magni- 
tude. Perhaps you have driven through 
regions which are below sea level (we 
have 'em in California) and you have 

-lo -9 -$ -7 -L -s -4 
♦ «•••• — • — 

again we have a practical application of 
and a physical meaning for negative 

So, we repeat, negative numbers may 
or may not have a rational meaning, de- 
pendent entirely upon the nature of the 
quantity to which they are applied. Thus 
a negative number of pencils is a false 
concept, but a negative temperature is 
understandable, for it simply implies a 
specified number of temperature units 
below an arbitrary reference tempera- 
ture. On the Centigrade scale, this 
reference temperature is understood to 
be the temperature at which water 
freezes, 0° Centigrade. 

From the foregoing it may be stated 

1. Negative numbers have a rational 
meaning only when they pertain to par- 
ticular phenomena or physical magni- 

2. When negative numbers do have 
rational meaning, they co-exist with a 
particular reference or datum point on 
the measurement scale in which they 
are used. 

To further illustrate our point, it 
would be possible to revise our method 
of denoting years in history. Now we 
write 50 B.C., or 1939 A.D. The refer- 
ence point in this system is, of course, 


nineteen hundred and thirty-nine years 
after our reference time. 

The conventional way of providing a 
visual idea of the relation between posi- 
tive and negative numbers is by dia- 
gram such as is shown in Fig. 1. The 
positive series of numbers start at zero 
and advance toward the right. The 
negative series of numbers start at zero 
and advance toward the left. The point 
0, then, corresponds to the reference 
point we have described. 

The number negative three or minus 
three is written — 3. The number posi- 
tive five or plus five is written +5. 
Often the + sign is omitted before 
positive numbers, but in such cases its 
presence is understood. But the nega- 
tive sign, — , is never omitted before a 
negative number. 

In arithmetic we have become ac- 
customed to thinking of the signs + and 
— as signs of operation, that is, + 
means addition, and — means subtrac- 
tion. They are also used to denote the 
same operations in algebra. But when 
we enter the algebra field these signs 
take on another significance. That is, 
+ and — continue to be used to indi- 
cate addition and subtraction in algebra, 
but these signs are also used to signify 
the nature of the quantity under con- 
sideration, whether positive or negative. 

For this reason algebraic numbers are 
often enclosed in parentheses to enable 
us to readily distinguish between the 
nature of the numbers and the opera- 
tions to be performed on the numbers. 
After dexterity has been acquired in the 
handling of positive and negative num- 
bers the parentheses may be omitted in 
many cases, but until that skill is at- 
tained the use of parentheses is recom- 

Let's try some specific examples in 
addition. Add positive seven and posi- 
tive two. This is written: 

(+7) + (+2)=+9 

The + sign between the parentheses 
is the sign of operation; i.e., addition. 

-3 -2 -/ O +| +2 +3 +4 L +£ +1 + y +g +<j +/o +tl 

noted sign posts which read: Eleva- 
tion — 20. The meaning is simply that 
that particular locality is twenty feet 
below the arbitrary reference level — sea 
level. And, too, one frequently sees 
sub-zero temperatures referred to as 
—5°, —10°, —15°, and so on. There 

the time of the birth of Christ. Keep- 
ing the same reference point we could 
justifiably write — 50 and +1939. Under 
such a revised system, mention of the 
year — 50 would be easily recognized as 
50 years before our reference time; and 
mention of the year +1939 would mean 

The + signs before the numbers them- 
selves are signs showing the nature of 
the numbers; i.e., both numbers are 

This operation for addition may be 
illustrated by reference to Fig. 1. Be- 
gin at the point on the scale occupied 

JULY. 193 9 


by the first number ( + 7), and move 
(+2) units from that point. This 
brings us to +9. 

Here's another: Add positive seven 
and negative two. This is written: 

(+7) + (-2) =+5 

Whereas before we started at (+7) 
on the scale and moved to the right, be- 
cause (+2) was to be added to ( + 7), 
now we start at ( + 7) and move two 
units to the left, because ( — 2) is to be 
added to ( + 7). This brings us, of 
course, to the point +5. 

And yet another illustration: Add 
negative seven and positive two. This is 
written : 

(-7) + (+2) =-5 

Here below are some more examples 
which will serve for practice. Each 
problem is written twice — once in the 
left-hand column, once in the right-hand 
column. The rigorous form of writing 
the problem is used in the left-hand 
column; that is, parentheses are used 
freely to help differentiate between the 
nature of the numbers and the operation 
to be performed upon the numbers. But, 
as has been stated, when a number is 
positive the + sign before it may be 
omitted as long as its presence is under- 
stood. Hence in the right-hand column 
we have written the problems with per- 
missible eliminations of some + signs 
and parentheses. 

(+2) + ( + 3)= + 5 
(+4) + (—2)=+ 2 
(—3) + (+3)= 
(— 6) + (— 6) =— 12 
(_7) + (+l)=— 6 
( + 5) + (-6)=- 1 

2+ 3 = 

4+ (-2) = 

—3+ 3 = 

-6+ (-6)=- 

-7+ 1 =- 

5+ (-6)=- 




- 6 

- 1 

These sums we have been finding are 
known as algebraic sums, for the signs 
of the numbers involved must be con- 
sidered as well as the magnitudes of the 
numbers. When sums are found in 
simple arithmetic — arithmetical sums — 
all of the numbers involved are always 
positive. But when algebraic sums of 
numbers are to be found these rules 
must be kept in mind: 

// the numbers have the same signs, 
determine the sum of their numerical 
values, and place the common sign be- 
fore the result. 

If the numbers have different signs, 
find the difference between their numer- 
ical values, and place the sign of the 
larger number before the result. 

If, for example, more than two alge- 
braic numbers are to be added, combine 
all the positive numbers to form one 
number, combine all the negative num- 
bers to form one number, and with the 

tAvo numbers thus obtained proceed by 
the rules above. 

(+4) + (— 3) + (+7) + (-6) = 

[(+4) + ( + 7)] + [(-3) + (-6)] 

( + 11) + (-9) 


An algebraic quantity formed by pre- 
fixing a coefficient to a letter or letters 
is known as a monomial. Thus la, 2b, 
4a 2 k, etc., are monomials. If the sym- 
bols following the coefficient are in each 
instance the same, we have what are 
known as similar ■ monomials. Thus 
6yb, 4>yb, — lyb, 2yb, are similar mon- 

When adding a group of similar mon- 
omials find the algebraic sum of the 
coefficients, and prefix this sum to the 
common letters. As an example : 

(+4kn) + (— 3kn) + ( + 7kn) = 
[4+7+ (— 3)]kn 
[11+ (— 3)]kn 

Often the simpler problems of finding 
the sum of a group of similar monomials 
can be performed mentally. Thus, in 
the first example given below, the sum 
of the positive coefficient is +12, 
sum of the negative coefficients is — 7, 
so the net sum of the coefficients is +5. 







— 6tm 

— 4tm 

— 6v 2 

+ 3v 2 
+ 2v 2 
— 4v 2 

3x 3 y 
— lx 3 y 
— 4x 3 y 
+ 9x 3 y 

5s 5tm — 5v 2 7x 3 y 

Now that we have laid the foundation 
for addition of algebraic quantities let 
us next consider subtraction of algebraic 
quantities. Here's the rule to remem- 

// any number b is to be subtracted 
from any number a, change the sign of 
b and add b to a. Showing applica- 
tion of this rule: 

( + a) — (+b) = (+a) + (— b) 
(+a)-(-b) = ( + a) + ( + b) 
(_a)-(+-b) = (-a)+(-b) 
(-a)-(-b) = (-a) + (+b) 
Hence the sign indicating the opera- 

N. Y. World's Fair Visitors 

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the facilities offered by I. P. in 
making more pleasant their visits 
to the New York World's Fair. 
Whether it be a matter of hotel ac- 
comodations, reservations for amuse- 
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or for any chore that will make 
one's stay in New York more pleas- 
ant, I. P.'s services are at your 

tion of subtraction, — , is changed to 
the sign indicating the operation of 
addition, +, when the rule for subtract- 
ing is complied with. Let us say that 
6=4 and a =6, and solve the above four 
examples with the substitution therein 
of those values. 


-(+4) = 

6+ (—4) = 



-(-4) = 

6+ 4 = 




-6+ (—4) =- 




-6+ 4 =- 

- 2 

Usually simple algebraic subtraction 
can be performed mentally saving the 
time required to write the process down 
in detail as we have done above. In 
the following examples the lower mem- 
ber is to be subtracted from the upper 
member. Remember the rule and try 



















Subtraction of monomials is an easy 
step forward. Change the sign of the 
coefficient of the monomial which is to 
be subtracted, and add that coefficient 
to the coefficient of the similar monom- 
ial; and then annex the common letters 
to the result. 

In the following examples illustrating 
application of this rule the lower mon- 
omial is to be subtracted from the sim- 
ilar upper monomial. Hence, in the 
operation, change the sign of the coeffi- 
cient of the lower monomial and add 
that coefficient to the coefficient of the 
upper monomial. 

19xy 4c 2 — 15sk 3r 12n 3 ab 
17xy ■ — 2c 2 lsk 3r — 7n 3 ab 


6c 2 


19n 3 ab 

We move along to a discussion of 
multiplication of algebraic numbers. 
The primary thing to remember here is: 
When two numbers of the same sign 
are multiplied, the product is positive. 
When two numbers of opposite sign 
are multiplied, the product is negative. 


(+m)X(— n)=— mn 
(— m)X(+n)=— mn 
(— m)X(— n) = +mn 

If we substitute 2 for m, and 3 for n: 

( + 2)X(+3)=+6 
(+2)X(— 3)=— 6 
(— 2)X( + 3)=— 6 ' 
■ (— 2)X(— 3) =+6 

It is suggested that the reader work 
out the following problems independ- 



ently. Place a card over the results, 
and when you have your own answers 
compare them with those given. 

— 4X 6 =—24 
9X— t =— 9t 

— 8X— 8= +64 

— kX— g=+kg 
14X— s=— 14s 

— a-X— b 2 - + a 2 b 2 

Before we proceed much further dis- 
cussing multiplication it is necessary to 
find out what happens when a given 
number raised to a power is multiplied 
by the same number raised to a power. 
In other words, what is the result when 
we have: 

a 2 Xa* 
This we know: 


a x = 


a 2 = 


a 3 = 


a 4 = 


a 2 Xa 

3 = aaXaaa 

= aaaaa 

= a 5 

=a 2+3 

a 3 Xa 

3 = aaaXaaa 

= aaaaaa 

= a 6 

_ a 3 + 3 


The foregoing analysis brings out the 
general rule for writing the product of 
several identical numbers, each of which 
is raised to a power. The product is 
the number with an exponent equal to 
the sum of the exponents. 

Suppose we are to find the product of 
the monomials 3r 2 y and 2ry 2 . 

3r 2 yX2ry 2 = 
3Xr 2 XyX2XrXy- 

We can rearrange the order of the 
factors without changing the value of 
the product. Thus: 

3r 2 yX2ry 2 = 
3X2Xr 2 XrXyXy 2 
6Xr 2+1 Xy 2+1 

Find the product of 2n. 3 ; 2 and — 4ni: 
2n 3 t 2 X— 4nt= 

2Xn 3 Xt 2 X— 4XnXt 
2X— 4Xn 3 XnXt 2 Xt 
— 8Xn 3+1 Xt 2+1 
— 8n*t 3 

Below are some more examples to try. 
Check your results against those given. 

6k 2 

12k 3 

— 2p 2 r 2 

— 6p 3 r 3 

— 9svw 

— 18s 2 v 2 w 

Our final topic in this second section 
is division of algebraic quantities. The 
important thing to keep in mind is: 
// the dividend and the divisor have 
the same sign, the quotient is positive. 
If the dividend and divisor have oppo- 
site signs, the quotient is negative. 

+ 8 +8 

=+2 =—2 

+4 —4 



—4 +4 

At this point it is necessary to inves- 
tigate what happens when a given num- 
ber raised to a power is divided by 
the same number raised to a power. In 
other words, what is the result when we 

a 4 

have: — 

a 2 

We know that a 4 — aaaa. We know 
that a'- — aa. Hence, by cancellation of 
identical factors above and below the 
division line: 

a 4 aaaa 

a 2 aa 
= aa 
= a 2 
= a' 



a u aaaaa 

a" aaa 

= aa 
=a 2 

_ a 5-3 

a 3 aaa 

a x a 
= aa 
= a 2 

= a 3 - 1 

Hence, in general : 

a m 


The foregoing analysis above brings 
out the rule for writing the quotient 
when the dividend and the divor are the 
same number, and the dividend and the 
divisor are each raised to a power. The 
quotient is the number with an exponent 
equal to the divisor's exponent subtract- 
ed from the dividend's exponent. 

With this rule in mind we can pro- 
gress to division of similar monomials. 
4a B 
=2a 6 - 2 

2a 2 

16a 3 b 2 


=8a 2 b 

— 14x s y° 

2x 2 y 7 

=— 7xy 2 

Relax — that's all for this section. 


"Color Correction' Denned 

There exists the widespread impres- 
sion that "color correction" refers to 
some mysterious adjustment or property 
of a lens which causes it to photo- 
graph different colors in their exact 
shades or intensities. This is not true. 
Faithful reproduction of natural color 
on color film is a function of the film 
itself, not of the lens. Any lens will 
photograph blue as blue, red as red, 
within the limitations of the film and of 
the exposure; but not every lens will 
photograph objects of all different 
colors with equally sharp, crisp detail. 

It is an optical law that different 
colors in a given scene will focus on 
different planes if the lens is not de- 
signed to correct for this principle. 
For example, with an inferior lens in 
the camera, everything that is red in a 
scene might photograph sharply and in 
great detail, while all yellow and green 
objects would be fuzzy or unsharp on 
the screen. But the lens that is color 
corrected with photograph objects of 
all colors with maximum sharpness, for 
it is designed to focus all colors as 
nearly as possible on the same plane. 

• Sharp Definition Paramount 

Color correction, then, is entirely a 
matter of sharp definition, all over the 
picture, and it is obvious that to say 
that a lens "will photograph color" 
means nothing at all. To know defi- 
nitely that a lens is highly color cor- 
rected is to be sure of the finest in 
color movies. 

Of importance is the fact that color 
corrected lenses are just as important 
for black-and-white movies as for color 
film. Even though black and white 
film records various colors in differ- 
ent shades of gray, if those colors do 
not focus sharply on the film, their 
gray images cannot be sharp. That is 
why lenses were color corrected long 
before the advent of natural color film. 
—Bell & Howell Co. 


RCA has renewed the contract to serv- 
ice the sound reproducing equipment in 
the more than three hundred houses oper- 
ated by National Theatres Amusement Co. 
Original deal was signed in 1936. Theatres 
covered by the service contract include 
those of the Fox West Coast, Evergreen 
Theatres, Fox Wisconsin Theatres, and Fox 
Intermountain Theatres circuits. 


Clifford E. Giesseman, formerly general 
manager of United Detroit (Trendle) Thea- 
tres, has been appointed Altec sales rep- 
resentative in the Middle West, with head- 
auarters at Detroit. 

JULY, 1939 


Process Projection Specifications 




SPEED (Basic): 

The optical system shall have a speed 
of F2.0 or greater. 

(Auxiliary) : The foregoing recommenda- 
tion should not be construed to mean that 
developments beyond a speed of F2.0 are 
not anticipated. On the contrary, an 
F1.6 system is to be expected in the 


Adequate lateral, vertical and longi- 
tudinal adjustment facilities shall be 
provided for all units of the optical 
system, irrespective of the projection 

The optical system shall contribute 
no noticeable color, and that same 
order of spectral uniformity should ex- 
tend to a wave-length of 3800 A". 

TEM) (Basic): 

All mirrors used in the mirror-type 
optical system shall be surfaced -with 
aluminum, or at least its equivalent. 

Primary Condenser 


The primary condenser shall be of a 
focal length to give a maximum amount 
of light output using an F2.0 system. 
(See "Speed, Auxiliary"). 


The condenser mounting shall be so 
designed as to give sufficient clearance 
within the lamphouse to allow for ex- 
pansion of the condenser due to in- 
crease in temperature during opera- 
tion. Protective devices should also be 
provided to eliminate destructive air 
currents from the condenser when the 
lamphouse door is open. (See "Ven- 
tilation of the Lamphouse"). 

(Auxiliary) : An attempt should be 
made to design a method whereby the 
lamp could be retrimmed without sub- 
jecting the condenser to drafts or sudden 
temperature changes. (See "Ventilation 
of the Lamphouse"). 

CONSTRUCTION (Auxiliary) : 

The element of the condenser nearest 
the crater should be designed and con- 
structed somewhat thicker than at present 
so that pitting of this condenser can be 
removed by regrinding and polishing as 

Condenser Relay Type System 


The relay condenser type system 

♦Note: It has been suggested that the use 
of an auxiliary thin quartz plate between the 
arc and the preliminary element of the con- 
denser might furnish a protection for this 
condenser element, provided too great a light 
loss is not introduced. 

shall be designed to permit as short a 
set-up as possible and still deliver the 
maximum amount of light with an F2.0 
beam or cone of light. (See "Speed, 


The condenser relay mount shall be 
so designed as to permit both horizon- 
tal and vertical adjustments in both 
directions with a suitable pitch thread, 
so constructed as to maintain their set- 


The mountings of the condenser sys- 
tem shall be designed to give sufficient 
clearance to allow for expansion of the 
condenser during temperature rises. 

APERTURE (Basic): 

A lens shall be provided with an 
aperture of F2.0 or greater. The screen 
brightness should be controlled by a 
diaphragm in the case of an excess 
quantity of light, provided such a de- 
sign could be made practical.* (See 
"Speed, Auxiliary"). 


The lens shall be panchromatically 

*Note: The relay condenser system, because 
it does not focus the crater of the arc on the 
aperture, gives a smoother illumination. Further- 
more, this system is not limited by ae many 
uncontrollable items as is the mirror system, 
such as the increase of heat, increase of size 
of lamphouse, etc., associated with increased 
speed of the mirror. 

Experiments have proven that it is possible 
to diaphragm certain types of projection lenses 
used in process work without having the dia- 
phragm actually in the lens. 

This diaphragm is located just in front of the 
front element. Tests with Bausch and Super- 
Cinephor lenses show that perfectly uniform 
light control is obtained with no trace of in- 
crease of existing vignetting or hotspot due to 
stopping down of the diaphragm at this position. 
The definition of the image improves greatly 
when the iris is stopped down. Further tests 
with other types of lenses must be made to be 
certain that this method can be applied to all 

Classifications in Report 

In order to clearly specify the relative 
importance of the various recommenda- 
tions included in the report, each sub- 
heading in each part is indicated by one 
of the three following classifications: 

BASIC — Recommendations so in- 
dicated incorporate definite require- 
ments and principles. (Printed in 
bold face type.) 

AUXILIARY — Recommendations so 
indicated are suggested methods of meet- 
ing basic requirements. (Printed in 
light face type.) 

ACCESSORY — Indicates optional spe- 
cial refinements which add to the ease 
of operation of equipment. (Printed in 
italic type.) 

corrected to conform as nearly as pos- 
sible to the correction of the best 
camera lenses ; that is, the lens should 
be corrected not only visually but 
photographically. The secondary spec- 
trum should be as flat as possible. 


The distortion shall be less than six 
parts in a thousand. 

(Auxliary) : It has been suggested that 
the foregoing basic recommendation on 
distortion be reduced if possible. How- 
ever, this should not be done at the ex- 
pense of other types of lens correction. 

FIELD (Basic): 

The definition, resolving power, 
coverage, and flatness of field shall be 
comparable, as nearly as possible, to 
good anastigmatic photograhic lenses. 


The lens shall be accurately con- 
structed so as to be centered both 
optically and mechanically. 


The Committee recommends that the 
following be adopted as standard for 
lens mount diameters and submitted to 
the American Standards Association for 
consideration for formal standardiza- 

1. Lenses of F2.0 and F1.9 focal ratios 
are of particular interest to the industry 
at the present time. Everything possible 
should be done to produce lenses of these 
speeds whose performance is satisfactory 
for background projection. All possible 
development should be made on F1.6 pro- 
jection lenses from 4" to 6" focal lengths. 
There will be a demand for this series 
when it is produced with sufficient cor- 
rection to permit its use in background 
projection work. 

2. Studios will use F2.0 and F1.9 lenses 
up to and including 4" ; focal length with 
the diameters that are adopted by the 
manufacturers as standard for theatre use. 
It is strongly urged, however, that the 
diameters of the F2.0 and F1.9 lenses be kept 
as consistent as possible and with as few 
changes in shell diameter throughout the 
series as is practical. The latter restric- 
tion applies also to any F1.6 lenses and 
may be developed. 

3. For lenses of longer focal lengths, 
the standard lengths shall be 5", 6", 7", 
and 8". All other focal lengths will be 
in the nature of special requirements, to 
be supplied upon individual studio order. 

4. Lenses of the F2.0, F1.9. or F1.6 
series with focal lengths of 5", 6", 7", and 
8" will maintain an outside barrel diameter 
of 4 1 / 2 "'. 

5. Lenses of an F1.6 speed will be in 
focal lengths of 4" to 6" inclusive. Lenses 
with focal lengths longer than 6" should 
maintain a constant lens diameter up to 

(Continued on page 26) 



Defining Light-Sensitive Cells 

ALMOST everyone has heard of 
the photo-electric cell ("electric 
eye"). Hardly a day passes that 
we don't read in the newspapers or 
trade journals of some interesting or 
unique application to which the "eye" 
has been put. This article discusses 
the various types of light-sensitive cells 
commonly referred to in the literature. 

There are available today four dis- 
tinct types of devices commonly termed 
"photo-cells," each of which differs in 
its functional characteristics as well as 
in its general physical construction. Be- 
fore discussing these in detail, we might 
consider what is a "cell," that is, what 
it is supposed to be and do. 

The expression "photo-cells" denotes 
any device which will react electrically 
to light. This term is too broad, since 
it entails the different types of cells, 
not all of which are true "photo-cells" 
in the sense of correct technical defi- 
nition, even though all are classified 
as light-sensitive cells. 

If the term "light-sensitive cell" were 
applied to all the four different types 
of cells as one device or product, it 
would be a more fitting name. Simply 
expressed, the term "light-sensitive cell" 
denotes, as already stated, a device 
which will react to light; whereas the 
term "photo-cell" relates to one speci- 
fic type or form of light-sensitive cell. 

The expression "light-sensitive cell" 
is a bit cumbersome, and the industry 
has been seeking for an expression that 
will be readily recognized not only by 
technicians but even by the "man in 
the street". To this end the expression 
"electric eye" has been popularly ac- 


cepted as denoting any type of device 
that is light-sensitive. 

Let us consider the derivation of the 
name "photo-cell." The word photo is 
derived from the Greek, and is known 
as phot or phos, meaning light, or 


The author of the appended article is 
a noted worker in the electronic field, 
particularly in that branch relating to 
light-sensitive devices, several novel 
types of which are the result of his 
efforts. His many contributions to the 
art are recognized throughout the 
world, the technical literature being 
replete with references thereto. 

'phao", to shine. From this we derive 
phosphor, a chemical element that 
shines, and phosphorescence, meaning 
to give forth light. 

In the case of the word "cell," we 
find that it is derived from the Latin 
cella, meaning a small room or cham- 
ber. Speaking in terms of electricity, 
it is understood to denote a device 
which contains two electrodes inserted 
in an electrolyte, generating a source 
of current (E. M. F.), a battery. The 
hue meaning of the word "battery," as 
generally understood, is where two or 
more cells are electrically connected 
in a circuit so that it will increase 
either the current or the voltage out- 
put, depending on how they are con- 

Now that we have a better under- 
standing of the nomenclature used, we 
are better able to consider the differ- 
ent types of cells available. 

• Photo-Conduction Cells 

In the technical literature the use of 
such terms as "bridge," "unit," "ele- 
ment," or "resistor" designates the de- 
vice we recognize as a photo-conduction 
cell. The- term "cell" in the present 
case is a misnomer, but since that name 
is universally employed we are com- 
pelled to use it in order to avoid 
further discussion of terminology. The 
reason that the term "cell" is incor- 
rectly applied here is because the de- 
vice does not generate a potential upon 
exposure to light. 

The photo-conduction cell consists of 
a metallic element or a compound of 
elements which when exposed to light 
will exhibit a change in its electrical 
resistance (Ohmic value) when con- 
nected in series with a source of cur- 
rent and an indicating meter. It is 
commonly known as a photo-resistance 
type of cell. 

There are two distinct types of con- 
struction: (1) the winding of two 

wires around an insulating medium, 
with the element, usually selenium, be- 
ing spread between the wires and an- 
nealed in order to render it light-sen- 
sitive, and (2) a glass plate on which 
has been deposited either gold, plati- 
num or silver, which is divided into 
two electrical portions by means of a 
sharp tool, with the selenium being 
deposited over the entire surface and 
properly annealed. Although no sym- 
bol has as yet been assigned to it, 
Fig. 1 is offered as typical of this de- 

• Photo-Voltaic Cells 

The terms "Becquerel effect" and 
"photo-voltaic cell" are used to dis- 
tinguish other forms of light-sensitive 
cells. Expressed simply, the photo- 
Altaic cell consists of two metals in- 
serted in an electrolyte (solution), and 
by exposing one of these electrodes to 
a source of light a potential is gen- 
erated. By way of illustration, it might 
be said that we have here in the most 
elemental form a light-sensitive battery, 
a chemical change taking place on the 
surface of the exposed electrode. 

The name Becquerel is very well 
known to scientific investigators since 
it was he who first observed the radio- 
active emanations of carnotite or pitch- 
blend which later proved to be radium. 
This investigator also discovered the 
electrical effect obtained by exposing 
the metal plates in an electrolyte, thus 
the term "Becquerel effect". The effect 
is also commonly known as the "photo- 
voltaic effect". The Becquerel effect 
was first observed as early as 1839. 

There are at the present time two 


known forms of photo-voltaic cells: (1) 
those in which the electrodes them- 
selves are light-sensitive, and (2) those 
in which the electrolyte and not the 
electrodes are light-sensitive. Only the 
former types are available on the open 

JULY, 1939 


market; the second type still is in the 
experimental stage of development. 

No accepted symbol has been as- 
signed to this type of cell. In Germany 
and in England Fig. 2 has been used 
to some extent as a symbol. Here the 
active metal electrode forms the posi- 
tive pole of the cell. 

• Barrier Type Cell 

The modern "barrier" cell is ac- 
credited to the efforts of C. E. Fritts 
who in 1881 deposited on an iron disc 
a film of selenium, and on this latter a 
translucent film of gold. 

At the present time there are two 
types of barrier cells available, differ- 
ing only as to the choice of base metal 
used and the active or sensitive film. 
These two types are (1) that in which 
a film of selenium is deposited on an 
iron disc and properly annealed in order 
to render it light-sensitive, and (2) 
that in which a film of cuprous oxide 
is formed on a copper disc at elevated 
temperature, with, of course, subse- 
quent chemical treatment in order to 
dispose of the cupric oxide which is 
found to be deleterious. There is then 
deposited on top of the selenium or 
cuprous oxide film a translucent con- 
ductor (electrical), so that contact 
might be taken off the back side of the 
base metal (iron or copper). 

The complete circuit then is effected 
by taking contact off the translucent 
conductor. The light-sensitive material 
(selenium or cuprous oxide) is sand- 
wiched in between the base metal and 
the translucent conductor. In the place 
of gold other metals may be used as 
the translucent conductor, for instance, 
silver, platinum, cadmium, etc. 

While the effect has been commonly 
known for more than fifty years, it has 
only recently been accepted in the com- 
mercial field and in the academic 
laboratories as an instrument. No 


scientific organization has formulated 
standards for these types of cells. 

In the United States no accepted 
symbol for recognizing the cell in a 
circuit has been designated. In Ger- 
many the symbol as seen in Fig. 3-A 
has been used in the technical litera- 
ture to a great extent, and since it does 

not appear to have similarlity to other 
types of cell symbols, it might con- 
veniently be used. In England and in 
the United States Fig. 3-B has been 
used to some extent, and in the United 
States Fig. 3-C has been used to a 
great extent. 



Other names assigned to this type 
of cell are (a) Sperrschicht (b) self- 
generating (c) barrier plane (d) photo- 
voltaic (dry type) ; (e) blocking layer, 
and (f) dry disc photo-electric. 

© Photo-Electric Cell 

The term "photo-electricity" in its 
broadest sense refers to "any electrical 
effect resulting from light." This is a 
very wide term and properly should 
only be used when and if applied to 
all forms of light-sensitive cells, and 
not to specific type or form. However, 
we are concerned in the present dis- 
cussion with that type of light-sensitive 
cell which corresponds to the "Hall- 
wach effect," that phenomenon in which 
electrons are driven off a given surface 
upon exposure to light. 



In 1888, Hallwach demonstrated that 
a negatively-charged body loses that 
charge when ultra-violet light falls upon 
its surface; but when positively 
charged, the body is not influenced by 
light. The earliest form of photo-cell 
usually consisted of a zinc plate freshly 
cleaned with sandpaper, etc., which 
acted as one electrode, and in front of 
it was placed a collector, acting as the 
second electrode. The intervening 
space was, of course, filled with air 
at. atmospheric pressure. The results 
thus obtained were poor, but it was 
demonstrated to the physicists at that 
time that light caused the flow of 
"particles" between the zinc plate and 
the collector. 

Elster and Geitel took up the work 
of Hallwach, testing a great number 
of the metallic elements. They soon 
discovered that "alkali metals," when 
freshly distilled into evacuated glass 
bulbs, would give rise to a much more 
sensitive cell than that previously de- 
scribed. Following that discovery, it 
was soon established that if these 

metals were treated by a brush dis- 
charge (electrical) in the presence of 
hydrogen, the alkali metal would be- 
come colored and simultaneously in- 
crease its sensitivity to light manifold. 
This was known as the "hydride" cell. 
A further development was an increase 
in its sensitivity by admitting a trace 
of a noble gas such as neon, argon, 
helium, etc. 

The next development concerns the 
reaction between the alkali metal 
(caesium) and oxygen, forming the 
corresponding caesium oxide. In this 
case the cell is formed by distilling 
caesium on metallic silver (plate), and 
oxidizing both the silver and the caesium 
to form the corresponding silver- 
caesium oxide, the modern form of 
photo-cell. To further increase its sen- 
sitivity, the cell has a trace of one or 
more of the noble gases. 

The photo-electric cell is the only 
type of light-sensitive cell that has an 
accepted symbol assigned to it. This is 
shown in Fig. 4, and is the work of 
the I.R.E. Standardization Committee. 

St. Louis L. 143 Election; 
High Court Appeals Set 

Officers named for St. Louis projection- 
ist Local 143 in an election ordered by the 
Circuit Court following decision which 
abrogated I. A. control of the union are 
as follows: Robert Tomsen, pres.; Wil- 
liam Robinson, v.-p.; 0. R. Myers, sec- 
treas. ; E. D. James, rec.-sec. ; Julian 
Anthony, sgt. at arms; trustees: George 
Hess, L. C. Chambers and Homer Tong. 

Election precipitates novel situation in 
which duly elected officers of a labor 
union will serve under the supervision 
of a receiver, recently appointed, whose 
tenure of office was not affected by the 

Scheduled for hearing before Missouri 
Supreme Court at its Sept. term is ap- 
peal of John P. Nick, I. A. v. p., and 
Clyde Weston, former b. a. of L. U. 143, 
from decision of lower court appointing 
a receiver for union. Similar hearing 
set for case of William F. Canavan and 
other intervenors, who sought to have 
lower court accept an appeal bond 
which would have automatically voided 
the receivership. 


An attractive 56-page catalog containing 
a complete listing of all RCA sound equip- 
ment for a wide variety of applications 
in the industrial, entertainment and edu- 
cational fields, has been issued by the 
Commercial Sound Section. All items in 
the extensive RCA line are indexed and 
cataloged with photographs, prices, speci- 
fications and general descriptions includ- 
ing possible uses. In addition, a compact 
guide for prospective buyers is included 
in an easy-to-read chart of six basic sound 
systems which, with extra equipment for 
special requirements, cover every stand- 
ard application. 



The Baird Theatre Television Receiver 



The appended article is an excerpt from a lecture delivered recently before 
the London Court of the Guild of British Kinema Projectionists and Techni- 
cians, through the courtesy of which it is reproduced here. The excerpt, while 
extremely general in nature, will serve to convey to projectionists some idea 
of the Baird theatre system, pending the publication in I. P. of a promised 
detailed exposition of the topic by Baird engineers now actively engaged in 
demonstration work in New York City. — Editor. 

AS IN the early days of sound pictures, 
a survey of the theatre will have to be 
taken. It will be necessary in order to 
determine the best position for the aerial 
to take field strength measurements and 
advise the best location for the equipment 
in the theatre. 

The radio signal sent out by the trans- 
mitter is picked up by an ultra short-wave 
receiving aerial of special design. It is 
necessary to have this erected as high as 
possible above the building and pointing 
towards the station radiating the signal. In 
addition, and in order to overcome any 
chance of automobile ignition interfer- 
ence, it is strongly advised to have the 
aerial as far away from the road as pos- 
sible. The signal received by the aerial 
is delivered to the theatre receiver through 
a low-impedance lead-in feeder cable. 

All-Electric, No Moving Parts 

The equipment is all electric, having 
no moving parts whatsoever, thus eliminat- 
ing mechanical breakdown risks, and is 
foolproof, compact and exceedingly simple 
to operate. It is comprised of two main 
units: projector unit, and extra high ten- 
sion rectifier unit. 

The projector unit is composed of two 
complete receivers and houses two pro- 
jection tubes, each having its own sepa- 
rate time base generator and scanning 
equipment, vision receiver and amplifier, 
sound receiver and power supplies. When 
receiving a program both tubes are run 
simultaneously, only one tube actually pro- 
jecting on to the screen. It is thus pos- 
sible to fade over from one tube to the 
other if necessary. 

The unit is placed in the auditorium 
and projects the picture directly on to the 
viewing screen. A special screen is em- 
ployed and is placed in front of the 
normal theatre screen. The projector is 
usually placed about 30 feet from the 
viewing screen. 

A special projection tube has been de- 
veloped by Baird having a very high 
vacuum and producing an extremely bright 
picture on its fluorescent screen. It is 
this picture which is projected on to the 
viewing screen via a lens. 

The Projection Tube 
The construction and functioning of the 
tube is very similar to the ordinary radio 
valve. The electrode assembly of the tube 
is carried by a glass pinch and consists 
of a filament which is the source of 
electron supply: a cylindrical electrode 
called the modulator, which has a similar 
function to the control grid of a valve 
and to which the vision signal is fed, the 
signal having been amplified ; and an anode 
or accelerator to which the electrons are 

In order that the electrons can reach 

the fluorescent screen, the anode is pro- 
vided with a hole through which they can 
pass. The purpose of the electrodes so 
far described is to provide a beam of 
electrons and to give these sufficient 
velocity so that they will strike the screen 
of the tube where their presence is made 
visible by causing the specially coated sur- 
face to fluoresce. 

The modulator, which is similar in 
action to the grid of a valve, varies the 
density of the electron stream so that the 
amount of light caused by their impact on 
the screen will act accordingly. The beam 
is made to swing from side to side and 
downwards line by line by applying suit- 
able magnetic fields which are created by 
placing coils round the neck of the tube 
which houses the electrode assembly. 

These coils are fed with electric impulses 
generated by the scanning circuits or time 
base generators. These impulses are syn- 
chronized with the pulses sent out by the 
transmitter and so cause the electron beam 
to travel across the screen in synchronism 
with the beam in the camera. Thus the 
picture produced on the screen will be an 
exact reproduction of the image projected 
upon the mosaic of the camera. 

Special E.H.T. Unit 

In order to ensure an adequate source of 
high voltage for the anode of the projection 
tube, a special high tension rectifier unit 
has been developed. This consists of a 
voltage doubling circuit, using two tubes, 
and is capable of giving an output of 60 
K.V. at 10 ma. The normal working voltage 
of the tube is 36,000 volts, 300 microamps. 

The tubes are mounted above the unit, 
each being supported by insulators, which 
are removable for transport purposes. Separ- 
ate transformers are arranged to heat each 
of the filaments. Both these and the main 
c.h.t. transformer, as well as all smoothing 
arrangements, etc., are immersed in one 
common tank filled with insulating oil. A 
safety or ballasting resistance is connected 
across the output supply of the e.h.t. trans- 
former in order to protect the winding, 

Excuse It, Mr. Barrows 

In reporting recently the election of 
P. A. McGuire and James J. Finn as 
honorary members of the Guild of 
British Kinema Projectionists and 
Technicians, I. P. stated that they were 
the only American members. Stanley 
T. Perry, Guild prexy, informs us with 
bated breath that we err grieveously: 
five years ago the estimable Thad Bar- 
rows, president of Boston Local 182, 
while in London was tendered honor- 
ary membership in the Guild. This 
circumstance definitely relegates Messrs. 
McGuire and Finn to kindergarten. 

should a short-circuit occur. The output is 
then fed via a control to the anode of the 
projection tube. 

The e.h.t. unit is housed in a safety cage, 
so that when the door of the cage is open 
the supply is automatically switched off, 
and the positive terminal grounded. Simi- 
larly, it is not possible to restart the equip- 
ment unless the door is correctly shut. The 
whole equipment is exceedingly economical 
to run, the total consumption being 2 k.w. 
which is equal to the current consumption of 
the average electric fire. It is designed t" 
work off a.c. 50-cycle mains, 200-250 volts. 

The equipment described is similar to that 
installed in various London theatres and is 
capable of producing a picture 15 ft. x 12 ft. 
in size, with a degree of brilliance which 
precludes any possibility of eyestrain 1 . 

Regarding the sound installation, two loud- 
speakers, each with its own amplifier, are 
provided which are capable of delivering 
15 watts undistorted signal to each speech 
coil, the signal being provided by the radio 
receiver contained in the projector unit. 

j Note: Projectionists may regard this as a 
phenominal achievement for the baby art of 
television, beset as it is with many and varied 
problems of illumination, in view of the fact 
that comparatively few motion picture theatres, 
including some in the de luxe class, have yet 
to attain this goal. — Ed. 

GoldE Oil-Drive Takeup 

A new oil-driven takeup has just been 
introduced by the GoldE Mfg. Co. Ac- 
curately machined, the takeup is a 
totally enclosed device filled with a spe- 
cial oil and permanently sealed. Not 
only will the viscosity of the oil not 
change, but the takeup will suffer none 
of the effects of dust, dirt, oil, lint. etc. 

When sealed this new oil-driven take- 
up is adjusted for reels containing 2500 
feet of film, and no adjustment is 
needed thereafter — an important advan- 
tage on a job where each projection- 
ist has his own likes and dislikes. The 
initial and final adjustment assures a 
complete lack of wear on sprockets or 

This GoldE takeup is adaptable to 
all makes of projectors for use with 
special V belt or regular round belting. 
Special models for chain drive are avail- 
able at slight extra cost. A separate 
Bodine motor drive assembly is now be- 
ing readied for production and will be 
announced shortly. Further details are 
available from the manufacturer at 1214 
West Madison St., Chicago. 

Many and varied projection acces- 
sories are described in a new catalog 
just issued by GoldE. Available to 
I. P. readers upon request direct to the 


Macon, Ga., Local 507 observed its 25th 
anniversary recently with a party that had 
50 guests marveling how a unit having only 
9 members could do such a bang-up job. 
Guests attended from Atlanta, Rome and 
Columbus, among whom was Cliff Clowers 
who addressed the then new local 25 years 
ago, and W. A. McKenna, who helped 
organize the unit and installed its first 
officers. The latter and Dan Holt, well- 
known minstrel man, were presented with 
gold cards. 

JULY. 1939 


New Academy Theatre Test Reels 

THE Research Council of the 
Academy of M. P. Arts & Sciences 
has followed up its recommenda- 
tion anent Standard Electrical Charac- 
teristics for the common types of theatre 
sound systems with various testing reels 
that should prove of great value in keep- 
ing these units up to peak performance. 
The Theatre Test Reel, of 1000 feet, 
contains representative examples of cur- 
rent recording from each of eight major 
studios which furnishes a quick check of 
overall quality. It contains both sound 
and picture, including a hi-range print 
which checks on amplifier capacity in 
relation to volume. Use of this reel 
demonstrates the inadvisability of having 
too much low-frequency electrical re- 
sponse which brings out noise reduction 
bumps, footsteps and parisitic low-fre- 
quency noises on the set. 

The material contained in the reel is 
not a sample of the best recording avail- 
able, but is typical of the average. 

Studios will, from time to time, submit 
new samples for inclusion in the reel; 
and all users will be given the oppor- 
tunity of purchasing new samples to 
be spliced into their prints. By rotat- 
ing and spacing this "substitution of 
samples" procedure, prints will be kept 
up-to-date at a minimum of cost, and the 
new samples will replace deteriorated 

• Two Frequency Reels 

The Academy , now has available two 
different frequency reels. The first termed 
the Secondary Standard Multi-Frequency 
Test Reel, serves for routine checking of 
theatre characteristics and contains the 
following frequencies: 
1000 300 2500 5000 

40 500 3000 6000 

70 1000 3500 7000 

100 2000 4000 8000 

The second, called a Primary Standard 
Multi-Frequency Test Reel, is intended 

for use in installation of new equipment 
or for the complete check of an electrical 
characteristic by equipment manufac- 
turers, servicing organizations, or studios. 
The Primary Standard Reel should also 
be used for those particular cases when 
more points on the curve are to be in- 
vestigated than might be necessary in a 
routine check. The following frequencies 
are included: 


























Academy projector balancing loops. This method of threading applies 

to all types and makes of equipment other than the exceptions illustrated 

in Figs. 2 and 3. Loop length — 81". 

Announcements before each frequency 
are included in both these reels to facili- 
tate their use. Negatives for these reels 
are made all in one piece, to eliminate 
possible flutter or printer trouble. 

For determining the acoustic response 
of the horn systems and of the audi- 
torium the Academy has made available 
Standard Warble Tone Test Reels. As 
in the M.-F. Reels, Primary and Second- 
ary Standard prints are available, in both 
variable area and variable density, each 
containing approximately the same fre- 
quency as are included in the M.-F. 
reels. Each frequency has a warble of 
± 5% on all frequencies, this degree 
of warble having been chosen so that 
standing waves will be minimized in the 

Through the use of a microphone in 
conjunction with an amplifier system and 
a sound level meter, the acoustic re- 
sponse of the sound system and audi- 
torium at the various frequencies can be 
determined. Under normal conditions at 
least five different microphone positions 
in the auditorium are used, and the read- 
ings are averaged to give the acoustic 
curve for the auditorium. 

To determine the acoustic response of 
the speakers, the conventional method 
of measurement involves the averaging of 
5 or more readings made with the micro- 
phone close to the speakers. However, 
in making these measurements care must 
be taken to select microphone positions 
which will not favor the response of 
either the high- or the low-frequency 
• Standard Buzz Track 

To check the lateral alignment of the 
scanning slit the Academy offers a Stand- 
ard Buzz Track. The opaque track is 
86 mils wide. On the picture side of 
the track there is a 300-cycle tone and 
on the sprocket side a 1000-cycle tone. 
These tracks are so spaced that if the 
scanning slit is properly placed and of 
the correct dimension, no tone will be 
heard from the reproducer; but if the 
scanning slit is improperly placed toward 
the picture side, the 300-cycle tone 
will be heard, and if misplaced toward 



the sprocket side the 1000-cycle tone 
will be heard. 

A loop prepared from this track is 
run in the equipment and the scanning 
slit laterally adjusted until no tone is 
heard. In making up these prints the 
track placement is held to within — 2 
mils of the correct position. This track 
thus provides a means of adjustment of 
the position of the scanning slit to the 
current positioning tolerances. 

After the scanning slit has been 
checked for proper dimension and place- 
ment, it is of course necessary to check 
the uniformity of illumination across the 
scanning slit, and for this purpose the 
Academy has made available a Standard 
Scanning Illumination Test Track, which 
contains 17 approximately equally placed 
1000-cycle tracks, each with an ampli- 
tude of 6.8 mils ± 1.6%. 

If the illumination on each track is 
constant, the output as measured with a 
VI meter will be constant; but if the 
illumination varies the amount of this 
variation may be read directly on the 
VI meter measuring the output. Of the 
17 different tracks, the outside two and 
the inside two fall outside of a correctly 
positioned 84 mil slit. Therefore, with 
correct scanning illumination only tracks 
3 to 15 inclusive will be reproduced at 
full output. The maximum allowable 
variation in output level is 3 db, that is, 
a tolerance of ± 1.5 db. 

After this track has been run and the 
readings plotted against the track posi- 
tion, the graph so secured indicates a 
necessity for correcting any non-uni- 
formity in the illumination. This correc- 
tion should be by adjustment of the ex- 
citer lamp rather than by changing the 
lateral adjustment of the slit. 

For the adjustment of rear scanning 
sound heads, that is, the Erpi TA 7400, 
there is available a rear scanning ad- 
justment track, which consists of an 
opaque 84-mil sound track whose center 
is ± 2 from the nominal center line of 
243 mils from the guided edge of the 

The Academy Standard 7000-cycle 
Film contains a 7000-cycle variable 
density recording at 2 db below 100% 
modulation, in which the film response 
level varies less than — ^4 db. This 
film is available to be used as a test film 
to adjust the focus and azimuth of repro- 
ducer optical systems. 

The Academy recommends the use of 
7000- rather than an 8000- or 9000-cycle 
track because of the fact that in most 
theatre reproducing systems the low-pass 
filter greatly attenuates these higher fre- 
quencies. When using either 8000- or 
9000-cycle tones for adjustment it is usu- 
ally necessary to remove the low-pass 
filter. However, at the request of a num- 
ber of cooperating groups in the field, 
a Standard 9000-cycle film with a re- 
sponse level varying less than ± ^ db 
is also available for special purposes. 

These various test reels have been 
made available as a result of tours of 
investigation covering the entire country 
made by Council members during the 
past year. Visits to hundreds of thea- 

tres indicate in most cases a lack of 
sufficient test film for the projectionist 
and service men to provide even routine 
adjustment of equipment. 

All of these reels are available through 
the Academy upon a cost price basis 
which in most cases, includes no nega- 
tive or recording time costs, these items 
having been furnished by the studios at 
no cost. 

• Projector Balancing Loops 

Tours of investigation by members of 
the Research Council having disclosed 
that many theatres had no means of bal- 
ancing their projectors for output level, 
it was decided to make available an 
easily used Balancing Film at a reason- 
able cost and with sufficient instructional 
information to enable the projectionist 
to check the volume level balance be- 
tween machines as part of his daily 
routine (Figs. 1, 2 and 3). 

Hundreds of these loops have been dis- 
tributed to the field. Data assembled 
indicated that the longest loop necessary 
in any equipment would be slightly less 
than 7 feet. The Balancing Films were 
therefore made up to consist of sufficient 
film for two such loops. An instruction 
folder sent with each set shows the 
proper method of threading the loops 

into each of the common types of repro- 
ducing equipment, and outlines the 
proper method of checking the volume 
level balance between the two machines. 

After the loops have been properly 
threaded, the machines are started and 
the volume output is compared by means 
of meter or by eax. The machines are 
then, balanced for equal loudness at 
identical fader settings by adjustments 
normally provided in the equipment. 

There has been some comment from 
the field regarding volume variation be- 
tween reels in the same release print or 
between different sequencs within the 
same reel, requiring fader changes in 
the theatre during the show. Tests con- 
ducted indicate that recordings balanced 
for reproduction on an equipment set to 
the S.E.C. will invariably require fader 
changes when played in a theatre ad- 
justed to a non-standard E.C. We con- 
sequently believe that a great deal of 
the volume variation encountered is a 
result of reproduction of product origin- 
ally recorded for the S.C. but played 
upon equipment set to a non-standard 

Listening tests have been conducted in 
a sufficient number of acoustically aver- 
age auditoriums to prove conclusively that 
present-day recordings are sufficiently 

This method of threading applies to RCA PS-24 and other later similar 
sound heads, used with any make of picture head. Loop length — 15*4:". 




alike to reproduce satisfactorily on an 
equipment set to the S.E.C. 

While there have been no radical 
changes in recording or reproducing in 
the last year, there has been gradual 
improvement in both branches. During 
the last year the idea as to what consti- 
tutes good sound may have changed 
within the industry. A theatre con- 
sidered to have good sound a year ago 
may not be so considered at the present 
time. Consequently, it is possible that 
more recent installations have been set 
1o the S.E.C. and that a 25% estimate 
may be low. 

Reel Code No. Price 

Theatre Sound Test ASTR-2 $25.00 

Primary Standard, Multi- 
Frequency Variable Area. APFA-1 $25.00 

Primary Standard, Multi- 
Frequency Variable 
Density APFD-1 $25.00 

Secondary Standard, Multi- 
Frequency Variable Area. ASFA-1 $17.50 

Secondary Standard, Multi- 
Frequency Variable 
Density ASFD-1 $17.50 

Primary Standard, Warble 

Frequency Variable Area.APWA-1 $25.00 

Primary Standard, Warble 
Frequency Variable 
Density APWD-1 $25.00 

Secondary Standard, Warble 
Frequency Variable Area ASWA-1 $17.50 

Secondary Standard, Warble 
Frequency Variable 
Density ASWD-1 $17.50 

Standard Buzz (Lateral 

Alignment) Track ABzT-1 $ 2.00 

Standard Scanning Illumin- 
ation Test Track A17P-1 $12.50 

Standard 7000-Cycle Film.. A7KC-1 3y 2 c ft. 

Standard 9000-Cycle Film . A9KC-1 3l/ 2 c ft. 

Rear Scanning Adjustment 
Track ARS-1 5c ft. 

Standard 1000-Cycle Balanc- 
ing Film ABL-1 50cea. 

Prints of all the Test Reels described in 
the foregoing paper or information regard- 
ing prices, etc., are available at the offices 
of the Research Council of the Academy of 
Motion Picture Arts and Sciences.* Code 
numbers have been devised for each type of 
reel, as indicated, for convenience in des- 
ignating the particular type desired. Prices 
are based upon cost and are f.o.b. Holly- 
wood, Calif. 

Inasmuch as no extensive stock of Test 
Films is carried on hand, a period of from 
five to ten days should be allowed for 
preparation, calibration, etc., of prints. 

*1217 Taft Building, Hollywood, Calif. 

Coast Jurisdiction Battles 

Two new threats to I. A. on the West 
Coast: (1) new organization named 
United Studio Technicians Guild of 

North America, claiming substantial por- 
tion of 12,000 studio workers now in 
I. A. ranks, appealed to N. L. R. B. 
for designation as exclusive bargaining 
agent. Guild officers and total member- 
ship thus far a deep, dark secret. (2) 
1. A. Local 659 (photographers) de- 
manded jurisdiction over all first 
cameramen, which amounts to demand 
that A. S. C. be chased. Latter outfit 
recently obtained five-year renewal of 
contract with producers for first camera- 
men, which have not been under I. A. 

Moderate Industry Gains Seen 
By Poor's Investment Survey 

Moderately improved operations will be 
experienced by the motion picture industry 
during the final half of 1939, although the- 
atre attendance and box-office receipts are 
expected to hold at levels only slightly in 
excess of last year, according to a recent 
estimate by Poor's. Reduced amortization 
charges on films recently released under the 
1938-39 schedule will allow the showing of 
better earnings — even should theatre at- 
tendance show no gain from the present 

Contrasting with this fairly satisfactory 
outlook, a combination of political factors 
are disturbing. In addition to the antitrust 
action are (1) the Neely "block-booking" 
bill, recently approved by a Senate commit- 
tee and (2) threats of a NLRB hearing on 
wages, strikes, and union activities. At this 
juncture, it is difficult to forecast the ulti- 
mate outcome of current and pending liti- 

As for "block-booking," arguments pro 
and con seem to be pretty well in balance. 
Whether its elimination ultimately would 
prove beneficial to the industry is anybody's 
guess. Increased competition and higher 
production costs would be a natural con- 

Current estimates are that total costs for 
the motion picture industry's 1939-40 prod- 
uct will be higher than in the season cur- 
rently closing, since more "A" and less "B" 
quality films are promised under present 
production plans. Unit costs also will rise, 
for the total number of releases will be 

Because prospects indicate no important 
increases in theatre attendance, the incen- 
tive for building new film outlets has been 
dampened in recent months. Some improve- 
ment may be witnessed later this year, how- 
ever, if the industry's prediction of another 
upswing in box-office receipts actually 


Appointment of Fred W. Wentker as 
assistant Photophone Division Manager, 
and of W. L. Jones as National Service 
Manager, has been announced by RCA. 
Wentker was formerly assistant manager 
of the Service Division, while Jones has 
been in charge of Photophone service 
activities. Edward C. Cahill. Photo- 
phone Division Manager, will continue 
to supervise the activities of the Na- 
tional Service Division. 

This method of threading applies to Simplex Four Star sound 
used with any type of picture head. Loop length — 26". 



Griffith-Dickinson Theatres Inc., has ap- 
pointed Altec to service sound equipment 
in 30 theatres in Kansas, Missouri, Iowa, 
and Nebraska. 




(Continued from page 10) 

erally is to begin by drawing in all 
terminal boards, if any, all tubes with 
their socket terminals, and all trans- 
formers with their binding posts or 
color-coded wires, as the case may be. 
Resistors and condensers are too numer- 
ous in most modern amplifiers to be 
added in advance of the wire lines: 
they would be put in inconvenient loca- 
tions that would needlessly complicate 
the work of drawing wiring, and are 
best inserted one at a time, as encoun- 

With the major parts drawn, some 
prefer to proceed on a strictly physical 
basis, starting, say, with a power trans- 
former, drawing all connections as they 
appear without regard to their elec- 
trical meaning. Others work on a cir- 
cuit basis. To begin with, perhaps, 
heater circuits are followed, and the 
appropriate arrowheads and designa- 
tions set down. So much is simple 
The plate supply line, with its many 
branches, presents greater difficulty. 
Grid bias connections come next (they 
are also comparatively simple) and 
speech circuits last. 

This method has the advantage of 
giving meaning to the work as it prog- 
resses, thus affording an additional 
check against possible error; but on the 
other hand it may lead into error. 
Consider the unusual electrical arrange- 
ment of the plate and grids of the 
phase inverter tube of Fig. 2. 

• General Remarks 

The completed drawing, whether of 
Fig. 1 or Fig. 2, is generally not very 
clear, even though accurate: it has 
been made with attention concentrated 
on wiring details rather than on drafts- 
manship and usually needs to be re- 
drawn to make it compact, clear and 
thoroughly useful. Errors sometimes 
creep into the redrawing because one 
thinks the worst is over and relaxes his 

Circuit drawings made in times of 
emergency are seldom complete. For 
example, if the trouble is known to 
be some fault in the exciter lamp wir- 
ing of soundhead No. 1, there is no 
need to trace out all the circuits of 
Fig. 1. Only so much of the wiring 
is traced as is needed to give a com- 
plete picture of that exciter circuit, ex- 
ternally and internally, back to the 
power source; and even this can be 
reduced if voltmeter tests are used to 
show that the fault lies, say, inside 
volume control amplifier No. 2— that is, 

Read These Reasons — 

Tops the Field Because — 


It Offers 

Better screen illumination regardless of make, size and type — Minimum cost 
in current and carbons: MORE LIGHT PER AMPERE! — Maintenance is 
negligible — Every lamp guaranteed mechanically for one year — Has every 
known proved improvement — Modern and simple to operate — Costs no more 
than lamps of inferior quality — Guaranteed by the oldest and largest manu- 
facturer of projection lamps — Practical for either the 500-seat or 5,000-seat 

At Independent Theatre Supply Dealers Everywhere 
In Canada: Dominion Sound Equipments, Ltd., Montreal, Quebec 


47-31 Thirty-Fifth St. 

Long Island City, N. Y. 

behind terminal 2 of that amplifier, 
which connects with No. 1 exciter lamp 
through amplifier No. 1. 

Similarly with Fig. 2: voltmeter tests 
nay show a defect in power supply to 
some one tube socket, of a nature that 
limits very narrowly the amount of 
wiring to be investigated, or even of 
such nature that no circuit drawing is 
needed, but only a voltmeter check of 
one or two resistors. In other cases. 

JULY, 193 9 

half the amplifier, or even all of it, 
may have to be drawn on paper before 
a given trouble is understood. 

The latter is especially true of the 
most difficult and aggravating of all 
internal reconstructions- — not an ampli- 
fier similar to that shown in Fig. 2. 
but a complex switching panel. The 
switches and terminals are drawn first, 
and the wiring added. A really intri- 
cate switching arrangement, of the type 


used with some installations, can make 
the work of drawing Figs. 1 and 2 
seem childishly simple by comparison. 
The ohm-meter is generally trust- 
worthy, hut the voltmeter-and-battery 
can give misleading results. If the bat- 
tery be of moderately high voltage, 
such as a 45-volt B battery, circuits 
containing electrolytic condensers may 
show different results according to the 
polarity applied; the changed reading 


IransVeiteK Wins! 

Wherever stamina and en- 
durance count . . . the motor 
generator type of current 
conversion easily demon- 
strates its superiority. 

Ask about the many other 
outstanding features of the 

Consult the nearest office of The 
National Theatre Supply Co.; in 
Canada, General Theatre Supply 
Co.; or write us 


12692 Elmwood Avenue 
Cleveland, Ohio, U. S. A. 

Exclusive Manufacturers 
of the Transverter 

that can follow simple reversal of the 
test prongs may be puzzling if this 
point be not understood. The volt- 
meter is also misleading in high resist- 
ance circuits (see I. P. for March, 
1937, p. 24, and for May, 1937, p. 22). 
It can be used effectively only when 
its limitations are understood and 
proper allowance made for them. 


(Continued from page 18) 

the 8" focal length at which point the 
speed of this group will converge upon 
the F2.0 series.* 

Light Control 

A heat-resisting diaphragm light con- 
trol shall be provided at a suitable 
point in the relay condenser system to 
control the intensity of the light out- 
put. This diaphragm must not affect 
the flatness of field. 

This diaphragm control in the relay 
type condenser system will allow car- 
bons to be burned at their correct am- 
perage and thus give the maximum 
efficiency and maximum steadiness in 
light output. In an equipment pro- 
vided with this control, it is recom- 
mended that the carbons be burned 
within ±5 amperes of their rated cur- 
rent, as shown by the following list: 

(Submitted by National Carbon Co., Inc.) 

13.6 mm. . x 22 Positive Amperes 

7/16" x 9 Orotip Negative 125 

13.6 mm. x 22 Super H. I. Positive 

%" x 9 Heavy Duty Orotip Negative 175 
16 mm. x 20 M. P. Studio Positive 

%" x 9 Regular Orotip Negative. . 150 
16 mm. x 22 Super H. I. Positive 

W 1 x 9 Heavy Duty Orotip Negative 195 

*Note: Since these two lenses operate in such 
close conjunction with the projection movement, 
it is recommended that lens manufacturers con- 
tact the studios to determine necessary allow- 
ances in the lens barrel to clear the projection 
movement employed. It is the hope of the 
committee that one type of projection movement 
will eventually be adopted as standard by the 
industry, thus alleviating the necessity for sev- 
eral styles of mountings. (See "Aperture"). 

(Submitted by Noris Carbon Co., Inc.) 

16 mm. x 20 Positive— Type A 200 

13 mm. x 9 Negative— Type B .... 225 
13.6 mm. x 22 Positive 

7/16'< x 9 Negative 175 


The design should include a means 
of projecting a single frame for lining 
up purposes, permitting as much light 
as possible to pass through the aperture 




these features! 

Oil Driven — Fully Automatic 
Sealed For Life — Fool Proof 
Positive Power — No Jerk 
Smooth Even Tension Throughout 
No Torn Sprocket Holes 
No Teeth Undercut 
No Adjustment — No Failure 
Absolute Safety 

For full information — see 


or write 


1214 W. Madison St., Chicago, Illinois. 

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without damage to the stationary film.* 


CAPACITY (Basic): 

Grids shall be designed for mirror- 
type lamps to have a capacity of from 
75 to 150 amperes. For condenser- 
type lamps the grid capacity shall be 
from 100 to 250 amperes. Both types 
are to be provided with 5-ampere steps 
and with a uniform resistance at each 
step throughout the whole range. 

(Auxiliary) : It has been suggested that 
the above conditions can be met by pro- 
viding 10-ampere steps with auxiliary con- 
trols of 5 amperes to fulfill the foregoing 
basic recommendation. 


Grids shall be designed of such ma- 
terial and of a type giving a minimum 
resultant temperature resistance coeffi- 
cient. (See "Light Variation"). 


Grids shall be built solidly and be 
compact, yet easily portable. 

A remote control operating from the 
control panel of the projector, to open 
and close the power supply switch, shall 
be provided. 


Grids shall be so designed that when 
used in conjunction with a mirror lamp 
a maximum starting current of 75 am- 
peres will be provided; and when used 
in conjunction with a condenser-type 
lamp a maximum starting current of 
100 amperes will be provided. This 
current should be held steadily for a 
minimum of 30 seconds, at which time 
the grid should provide an easily oper- 
ated means for raising the current to 
its proper pre-determined operating 
value. (See "Light Control"). 

(Auxiliary) : The use of a switch arranged 
to first provide the proper starting or heat- 
ing current and then by one switching 
operation the proper operating current, has 
been suggested as one method of meeting 
the foregoing basic recommendation. Such 
a pre-heating arrangement would aid in the 
most effective use of the grid during the 
start of operation. (See "Line Switch 
Control") . 

CONTACTS (Basic): 

The contacts of the grid shall be so 
designed that the grid will give an easily 
operated method of resistance change 
and provide good electrical contacts, 
the efficiency of which will not vary 
over a period of time. 

(Auxiliary) : For grids designed to be 
used in conjunction with a projector equip- 
ped with a light control diaphragm (see 
"Light Control") the inclusion of a locking 
device has been suggested which, after a 
resistance change is made, gives a positive 
contact, rather than a contact of the rheo- 
stat or potentiometer type. 

*Note: An auxiliary light source of sufficient 
intensity to permit lining up should be provided. 




The increasing number of color films creates a 
new problem for you. A B.&L. Super-Cinephor Projection Lens on 
your projector helps you solve this problem. If your audiences are to 
see color films exactly as they were recorded, with every color in 
sharp focus . . . you'll need a color-corrected projection lens. 

Super-Cinephors are fully color-corrected . . . 
and in addition, are the first true anastigmats for projection ... a fact 
which means that on even the largest screens you can be sure of 
critical definition right to the edge ... in black and white or color. 

Write for complete information. Bausch & Lomb 
Optical Co.. 616 St. Paul St., Rochester. N. Y. 

"One new patron a day will pay for 
a Super-Cinephor in a year" 




An all-electric slow-motion camera cap- 
able of taking 80,000 pictures per sec- 
ond has been developed in Germany, re- 
ports the U. S. Department of Commerce. 

Known technically as a "stroboscope," the 
camera is designed primarily for technical 
and scientific research. Although other 
methods in use take individual exposures 
at a faster rate, the new stroboscope 
actually takes many more exposures per 
second through the subdivision of each 
individual exposure. 

80,000 Exposures a Second 

The basic principle of this stroboscope 
is a disc of rotating lenses that eliminates 
the shutter. Exposures are actually made 
only in the status of "optical equilibrium." 
To increase the number of exposures 
taken, a rotating disc moving counter- 
clockwise is arranged in front of the 

rotating lenses. This subdivides one ex- 
posure into 2, 4 and 8 narrow strips and 
thus permits the increase of the number 
of exposures taken to a maximum of ap- 
proximately 80,000 per second. 

Among the pictures shown was the 
movement of warm air circulating in a 
heated room taken without the aid of 
smoke. This was done by means of the 
mirage effect of different temperature air 
strata. The discharge of electric sparks 
over insulators and photographs of flying 
bullets hitting suspended steel wires were 
also shown. Pictures of flying bullets 
clearly showed the air waves in front of 
the bullet and the movement of the severed 
wire, according to the report. 

JULY, 1939 





Forest Rectifiers are more than 
just a collection of features! 
They are designed for motion pic- 
ture projection and are built to 
'take it'! Priced to enable more 
exhibitors and projectionists to own 
real protection and economy. There 
is a Forest Rectifier for every 


All Forest Products! 

• FOREST Thermionic Rectifying Tubes, 7%-lS 
amperes. Built to rated capacity, with high 
safety factor. Guaranteed Performance. 

O FOREST Low Intensity RectiBers. Type LD 
15-15 DC amperes and Type LD 30-30 DC am- 

• FOREST Bulb Rectifier for Suprex, Simpli- 
fied High Intensity or Low Intensity projection. 
Type LD 60—3 phase, 220 volts, 30-60 DC 

• FOREST Magnesium-Copper Sulphide Recti- 
fiers. Designed for Suprex or Simplified High 
Intensity projection. 5 models — 30 to 100 DC 
amperes, all for 3 phase operation. Using ex- 
clusively the P. R. Mallory rectifying units. 
Made in the Forest "Twin" models. 


in All 

Key Cities 

Forest M.C.S. 
"Twin" Rectifier 

«•..;«»« RECTIFIERS 

New Rectifer Fuse Indicator 

PROJECTIONISTS will welcome the 
advent of the Forest Fuse Indicator 
which, using Neon glow lamps in a 
special circuit designed for connec- 
tion to a 3-phase, 220-volt a.c. line, 
will give positive indication of a blown 
fuse or other open connections in the 
line which give rise to single-phasing 
of the rectifier. 

A blown fuse should be replaced 

the rectifier units and are connected in 
the secondary circuit of the rectifier 
between the transformer and the units. 
A blown fuse in this circuit will not 
be shown by the Fuse Indicator. A 
positive indication of a blown second- 
ary fuse will be given by a drop in 
amperage at the arc being supplied by 
the rectifier in which a fuse is blown. 
There will also be visible on the screen 


o Indicator 


n \ 




Conduit or BX 

Mounted on Box 

Mounted Separately 

immediately, as severe overload will re- 
sult from continued operation of the 
rectifier with the line in this condition. 
Spare tested fuses should be kept on 
hand at all times. 


a flicker or change in light intensity 
when the affected rectifier is in opera- 
tion; whereas a blown line fuse will 
affect both arcs. 
When single rectifiers are installed, 

Fuse Indicator 



No. 2 

To Equipment 

Within the rectifier cabinet are two 
fuses for each rectifier — two sets of 2 
fuses each in the twin unit, and one 
set in each single machine. These 
fuses are installed for the protection of 


a separate Indicator should be con- 
nected to each line switch for proper 
protection. A single Indicator is suffi- 
cient for the twin machine. In all 
cases the Indicator should be installed 



For all projectors and sound equipments 

All take-ups wind film on 2, 4 and 5 inch hub reels. 
Silent Chain Drives 


For perfect rewinding on 2000-foot reels. 


31-45 Tibbett Avenue New York, N. Y. 




where it will be readily visible from 
the operating position. 

• Installation Procedure 

The Indicator should be installed at 
the switch box controlling the equip- 
ment to be protected, either by direct 
mounting on the switch box with con- 
duit nipple supplied, or by means of a 
separate junction box connected to the 
switch with conduit or BX if room is 
limited. This line of course may be 
extended to any length to place the 
Indicator where it is readily visible. 
Fig. 1 shows this installation. 

Each unit is supplied with color- 
coded wires long enough to reach 
switch connections if mounted directly 
on the switch box. If connected as 
shown in Fig. 2 the lamps will not only 
indicate a blown fuse but will also 
show which fuse is blown. Connected 
in this manner both glow lamps will 
light when the switch is closed. If 
glow lamp No. 1 does not light, it is 
an indication that fuse No. 1 is blown; 
No. 2 lamp out indicates No. 2 fuse 
is blown; and both glow lamps out in- 
dicate No. 3 fuse blown. 

The Forest Indicator will also show 
a blown fuse elsewhere in the line be- 
tween the switch box and the meter, 
but will not indicate which fuse is 
blown unless all wires leading from 
the meter are properly identified. The 
lamps used in the unit are G.E. Neon 
glow lamps type G-10, 1 watt, and are 
readily obtainable from any electrical 

Complete installation and operating 
instructions are given on the card 
accompanying each Indicator. This 
card should be mounted on the wall 
near the Indicator for ready reference. 

A.F.M. Says I. A. Grabs Jobs; 

Wants Aid on Theatres 

A.F.M. Convention instructed execu- 
tive board to confer with I. A. relative 
to alleged attempt of latter to extend 
jurisdiction by moving in on spots — 
cafes, hotel rooms playing bands, radio 
stations, dog tracks, symphony halls, 
dance halls, p. a. systems — which mu- 
sicians feel belong to them more so 
than to I. A. Both organizations parties 
to mutual assistance pact of long stand- 

A.F.M. also wants movie producers to 
hire union musicians in at least all 
producer-controlled theatres, but in no 
event to extent of not less than a total 
musician wage of five million annually. 
Failure to comply with this demand 
would mean that A.F.M. would invoke 
I. A. pact and request latter to refuse 
service in affected theatres on and after 
Sept. 4 next. 

Govt. Suit Threat Nixed L.U. 

306 New York Strike 

Threat of criminal prosecution averted 
recent N. Y. Local 306 projectionist 
strike, it was revealed by testimony of 
asst. U. S. attorney general Thurman 





Nothing less than a picture v" 
depth and definition, one which 
brings out delicate details and 
fairly sparkles with realistic effect, 
is acceptable today. 

Exhibitors everywhere are credit- 
ing Strong Arc Lamps for giving 
them this improved projection. 

You, too, can enjoy the economy 
of using these modern lamps. Their 
higher efficiencies result in a tre- 
mendously increased volume of light 
without a corresponding increase 
in operating costs. 

For sale by Independent Theatre 
Supply Dealers everywhere. Dem- 
onstration in your own theatre, 
without obligation. 

Write today for free catalog on 

Strong unconditionally guaranteed 

products — your guide to better 



Export Office: Boom 2002, 220 W. 42nd St, New York Ciiy 

How Many? 

Was this copy dog-eared when it came to you? How 
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You would receive a clean, fresh copy if you had a 
personal subscription — and you wouldn't have to 
wait — you would be first to read it. 

Use coupon helow. 

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□ 1 year — 12 issues — $2.00 

□ 2 years — 24 issues — $3.00 
Foreign: Add 50c per year. 

Enter my subscription for 

Name . . 
City ... 


JULY, 1939 


Arnold before a Senate committee. 
L. 306 threatened city-wide strike if pro- 
ducers did not refuse to service some 
70-odd non-306 theatres. Said Arnold: 

"Recently the movie people came in 
and complained that the projectionists' 
union in New York was going to strike 
and close many of the picture houses in 
New York unless they (the producers) re- 
fused to furnish films to the largest non- 
union independents. It was to be a 
secondary boycott. 

"We called the labor union down and 
they said, 'Well, we think it is all right. 
We believe that Mr. Justice Brandeis' dis- 
senting opinion in the Duplex case is now 
the law, with the new (Supreme) Court.' 

"I said, 'I do not know anything about 
that. It may or may not be. I only 
point out to you one thing, that we can- 
not give you a free injunction ride to the 
Supreme Court if you happen to be wrong 
about this thing; and I think you are. In 
this particular case, it means criminal 

"The strike was ended; and everybody 
is going along perfectly happy." 

mm. standard release prints to 16 mm. 
was scored by A. T. O. 

Projectionist Day at Fair 

Projectionist Day will be observed 
with special ceremonies at the New 
York World's Fair on a date early in 
September. Joe Basson, head of Local 
306, has appointed a committee on 
arrangements consisting of George Ed- 
wards, Otto Kafka, C. Eichhorn and 
P. A. McGuire. The active participation 
of all locals in the U. S. and Canada 
will be solicited, at least to the extent 
of sending a representative. I. A. offi- 
cials will participate. 


Assoc. Theatre Owners of Indiana re- 
ports that 198 towns are being serviced 
by 16 mm. transient exhibitors, as con- 
trasted with the 447 legitimate movie 
houses in the State. Reduction of 35 

Your Iheatre 

needs this 

• No longer need you be in doubt about your projection 
equipment delivering highest possible quality results. These 
reels, each 500 feet long, are designed to be used in testing 
the performance of projectors. 

• The visual section includes special targets for detecting 
travel-ghost, lens aberration, definition, and film weave. 
The sound section includes recordings of various kinds of 
music and voice, in addition to constant frequency, constant 
amplitude recordings for testing the quality of reproduction, 
the frequency range, the presence of flutter, and 60-cycle or 
96-cycIe modulation, and the adjustment of the sound track. 

• For theatres, review rooms, exchanges, laboratories 
and wherever quality reproduction is desired. These reels 
are an S.M.P.E. Standard, prepared under the supervision 
of the Projection Practice Committee. 

"Invaluable. The finest technical contribution to the projection 
field since sound pictures were introduced." — HARRY RUBIN, 
Director of Projection, Publix Theatres. 

"No theatre that serves its patrons well should be without these 
test reels. Simply great."— R. H. McCULLOUGH, Fox West 
Coast Service Corp. 

"Eliminates all excuses for poor reproduction. Projectionists 
know just where they stand through the aid of these reels. I 
recommend them unqualifiedly."— THAD BARROWS. Publix 
Theatres, Boston, Mass. 

Price: $37.50 Each Section 
Including Instructions 

Address i 


Hotel Pennsylvania New York, N. Y. 


Projectionists at the Irvin Theatre, 
Bloomington, 111., recently walked out on 
an evening performance, occasioning re- 
funds to a large audience. Complaint 
was lack of ventilation in projection room 
and demand for more fans. Several fans 
v/ere installed in room the following day, 
and the crew returned to the job. 


Projectionists often suffer from eye-strain, 
and it is obvious that a treatment to re- 
duce the irritation plus an expedient to 
remedy the cause is the solution to the 
problem. A doctor prescribed for one 
projectionist the following solution: 

Concentrated boric acid 2 parts 

Camphor water 1 part 

Rose water 1 part 

Shake thoroughly. Bathe the eyes, using eye- 
cup, morning and night. Don't let up the 
treatment when the condition improves. 
This may not work for everybody, but it 
benefitted considerably one man. 

To cut down irritation use glasses that 
have a tinted lens, to reduce the irritating 
waves that are harsh on the eyes. A lense 
ground with a slight convexity, called a 
toric lens, will reduce further chances of 
glare. Consult your optician regarding the 
proper choice of lens. 


A superior film developer compound was 
described by J. R. Allburger, of RCA, at 
the recent S.M.P.E. convention. This new 
compound will make possible more faithful 
development of the sound track and picture 
negative, with uniform results for all prints 
released to the theatres. Ordinary develop- 
ing compounds must be replenished fre- 
quently during the developing process and 
the balance of the chemical formula is 
likely to be disturbed in such a way as to 
introduce variations in the quality of the 
finished film prints. In preliminary tests, 
the new RCA "Aluminate" developer proc- 
essed six times as much film footage with- 
out replenishment as did ordinary developer. 

Besides economy of chemical costs, the 
new Aluminate developer was said to have 
a hardening agent which serves to protect 
the emulsion on the film against scratches 
and abrasions from usage and handling. 


Since the death, by burning, of several 
projectionists in N. Y., State troopers have 
been checking closely the condition of thea- 
tres in small communities and have or- 
dered the closing of several until construc- 
tion changes were made. Enforcement of 
safety regulations in buildings is vested in 
the State Police where no local supervising 
officer or body exists. 

A number of small houses do not qualify 
from every angle of safety, some observers 
assert. A very rigid enforcement of safety 
provisions might close many of them. 


Altec Service Corp. has created a new 
service territory in the Philadelphia district, 
comprising eastern shore of Maryland, Dela- 
ware, and Virginia. W. M. Schubert will 
supervise from Dover, Del. 






A New Amazing Way 

# Will not thicken, spoil or 

# Retains its full strength to 
the last drop^—even when left 
uncovered. Requires no thin- 
ning agent. 

# Firmly binds all film — 
nitrate, acetate, color stock. 

9 Goes twice as far as 

T TSERS of film cement, and particu- 
larly projectionists, will welcome 
Film-Weld — because it is not a cement! 
Developed in the chemical laboratory 
of a mid-Western university, Film- 

There is a convenient size for 
every user 

1 oz. bottle 25c 

4 oz. (Special theatre size) 50c 

Vi pt. can 75c 

1 pt. can $1.25 

to Splice Film 

Weld is as clear as water and just 
as thin. And it never hardens . . . 
nor requires any thinner. 

Film-Weld is compounded to meet 
the exacting demands of modern pro- 
jection — higher film speed and intense 
heat of the new arcs, which impose 
severe strain on the film. Film 
cement was never designed to meet 
these conditions. 

Film- Weld is used the same way as 
old-fashioned cement — but it binds the 
film instantaneously in a splice that 
is ready for immediate use. The splice 
is several thousandths of an inch less 
thick than that made with cement, yet 
it is several times more binding. 


Try a dab of regular cement on 
paper, cloth, rubber, leather, or even 
on your fingers — it sticks there all 
together, like glue. Now try Film- 
Weld the same way. It doesn't even 

make your fingers sticky. But on film 
it works wonders. 

Here, at last, is a compound that is 
equally efficient on ALL film — nitrate, 
acetate, and all color prints. Forget 
the cork . . . leave it exposed con- 
tinually ... it will never thicken and 
will maintain its consistency and 
efficiency down to the last drop ! No 
thinner is ever required. 

Developed for the exacting needs of 
the film laboratories and exchanges, 
Film- Weld is now available for 
theatre use. Projectionists will wel- 
come the Vi pt. bottles especially de- 
signed for their convenience. Film- 
Weld is now being used by the largest 
theatre circuits in the country. 


Buy a bottle of Film-Weld and 
make your splices for a week. Then, 
if you still prefer the old-fashioned 
cement, return the unused portion of 
Film-Weld to your dealer and receive 
your money back. 

Film-Weld is sold by all theatre supply dealers on a money -back-ij- 
not-satisfied basis. Order Film-Weld on your next regular visit to 

your dealer. 


1241 South Wabash Ave. 

Chicago, Illinois 







r ^ 

,-, *v 



# First in our tiny shops, then in our tre- 
mendous plant, originated or developed 
every important advance in projection that 
made possible the motion picture industry. 




• ••• 



\Fl.i a , t 

£?? "Or CO/^ 

cp ip joo 



O iwJ 









25c A COPY • $2 A YEAR 

Used for 
High Fidelity 
Long Life 




Get spare photocells for 
every projector. Order 
from your supply dealer! 


1731 Belmont * Chicago 


Visitron cells are available for every type of sound projec- 
tion equipment. Theatre supply dealers can advise the 
correct cell for your equipment. Buy from your supply 
dealer. If you wish to have your old cells tested without 
charge, write to G-M Laboratories, Inc., for instructions for 
shipping. Information furnished promptly. 


The New and Wholly Different 


Does Not Touch the Film or Reel! 

(Patent Pending) 

1. Regular spring lock nut. 

2. Signal clamped to magazine 

3. Fibre disc. 

4. Lock nut for fibre disc. 

The story on this new and unique device is as simple as the unit itself. 
Here it is: 

1. Does not touch the film or reel. 

2. It is strictly mechanical and requires no batteries, no transformers, 
no governors, and no pre-setting by the projectionist. 

3. Is not dependent upon any change in the normal smooth operation 
of the projector. 

4. It is installed within 5 minutes, requiring no drilling. 

5. Once installed, forget it — as was conclusively demonstrated by 
1200 tests under practical conditions in various projection rooms. 

INSTALLATION: A multiple-sided fibre disc (3 in photo to the left) 
is mounted on the end of the upper magazine shaft and is held in place 
by the locking nut (4). The signal is clamped onto the outside of the 
magazine, the vibrating arm resting against the fibre disc. This arm is 
held against the disc by a spring. Mounted on this arm is a vibrating reed 
having a lead weight on its end. 

OPERATION: As the film in the upper magazine decreases, the reel 
naturally revolves faster, as does the shaft. When 115 feet of film remain 
on the reel, the fibre disc on the shaft end is revolving at just the correct 
speed to impart the correct frequency to the vibrating reed so as to cause 
contact with the bell. This frequency of vibration continues for about 15 
seconds, during which time the lead hammer is contacting the bell. 

After 15 seconds the fibre disc is revolving so fast that it has exceeded 
the vibration frequency at which the bell will be contacted — thus the bell 
stops ringing. Thus, 75 seconds before the end of the reel the bell begins 
to ring, continuing distinctly for 15 seconds, after which period of time it 
ceases. The duration of the bell-signal can be increased or decreased about 
15 seconds by simply moving the arm to either the left or the right. 

Install it and Forget it — 
It is Always Set! 

Projectionists are enthusiastic about this new and novel Strong Reel-End 
Signal on the score of its simplicity, absolute reliability of operation, ease 
and speed of installation — no less than because it does not touch either 
the film or the reel. The first lot of Strong Reel-End Signals was quickly 
disposed of to several large theatre circuits, including Paramount, which 
companies approved the unit immediately upon demonstration. 

Made by the manufacturer of the famous Strong Zipper Changeover, 
this Reel-End Signal is sold on the same basis — your money refunded if 
you are not thoroughly satisfied. 

The Strong Reel-End Signal can be used on all projectors which use 
standard 4-inch hub reels. It is distributed by all theatre supply dealers. 
The next time you visit your favorite supply dealer ask him to demonstrate 
how this unique Strong Reel-End Signal will afford you 
positive protection on all change-overs. Once you try 
this unit you will never again be without it. Orders 
filled promptly. 



If ill 


m 4 :! 


Makers of Precision Projection Equipment for 25 Years 

908 South Wabash Ave. Chicago, Illinois, U. S. A. 









The even color balance of high 
intensity projection light gives 
natural and pleasing screen re- 
production of color features. 
Lack of blue and excess of 
red in low intensity projection 
light distort the natural hues 
and beauty of color features. 

■ ■ ■■■■—'• i 



AND I A"" 






Simplified High Intensity 
projection provides 2.7 
times the volume of 
screen illumination ob- 
tained from low intensity 
lamps. This gives a clear 
screen image at a com- 
fortable level of general 

Simplified High Intensity 
lamps provide 2.5 times as 
much screen light per watt 
as low intensity. You cannot 
afford to retain low intensity 
projection when a few cents 
more per day will give you 
snow white projection light in 
more than twice the volume. 

■BHUMBH.;: :_. i 1 1 1 1 1 1 1 I 1 1 <l I 1 1 M I. 


. .... , .. ...... ... ..,,.... .. . . . 








/oooooooooooooooou uooaDoa[lannnnnooaa oo_ 
The words "National" and "Suprex" are trade-marks of National Carbon Company, Inc. 



Unit of Union Carbide HIM and Carbon Corporation 

General Offices: 30 East 42nd Street, New York, N. Y. 



Edited by James J. Finn 

Volume 14 

AUGUST 1939 

Number 7 

Index and Monthly Chat 5 

Film Projection by Mercury- 
Vapor Discharge Lamps ... 7 
G. Heller 

S.M.P.E. Projection Practice, 
Exchange Committees Report 10 

Fundamentals of Mathematics, 

III 11 

George Logan 

Clinical Note for Theatre Man- 
agers 12 

The H-S Ail-Metal Arc Reflec- 
tor . 14 

C. E. Shultz 

Process Projection Specifica- 
tions, III 16 

Report by Academy of 
M.P. Arts and Sciences 

Industry Ills Many and Serious 17 
James J. Finn 

Projectionist Day at New York 
World's Fair 17 

I. A. -Equity Row Threatens 
Amusement Field Tieup ... 21 

News Notes 

Technical Hints 

Miscellaneous Items 

Published Monthly by 



Circulation Manager, Ruth Entracht 

Subscription Representatives 

Australia: McGills, 183 Elizabeth St., Melbourne 
New Zealand: Te Aro Book Depot, Ltd., 64 Courtenay Place Wellington 
Encland and Dominions: Wm. Dawson & Sons, Ltd., Pilgrim St., London, E. C. 4. 

Yearly Subscription : United 
States and possessions, $2 (two 
years, $3) ; Canada and foreign 
countries, $2.50. Single copies, 
25 cents. Changes of address 
should be submitted two weeks 
in advance of publication date to 
insure receipt of current issue. 
Entered as second-class matter 

February 8, 1932, at the Post 
Office at New York, N. Y. under 
the act of March 3, 1879. 
Contents copyrighted 1939 by 
James J. Finn Publishing Corp. 
International Projectionist 
is not responsible for personal 
opinions appearing in signed 
articles in its columns. 

Monthly Chat 

THE answer to the query "What's 
new?" concerning the projection field 
during the past half year would neces- 
sarily have evoked the reply, "Nothing, 
nothing at all," so dull and dreary has 
been the picture relative to activity by 
manufacturers, to whom the field must 
look for technological advances. But sud- 
denly ("and the birdies sing") the wind 
shifted and a shipload of new develop- 
ments made port. To enumerate: 

The new series //2 lenses made by 
Bausch & Lomb lias been mentioned here- 
in, but particulars are lacking. Now, for- 
sooth, along comes International Projec- 
tor Corp, with a socko new projection 
room installation, complete from base to 
stage speakers and including arc lamp, 
for the smaller theatres. (This lamp, in- 
cidentally is a low-intensity job. The eco- 
nomic reasons for this unit we savvy 
but the technical reasons elude us.) 

Mention of lamps brings to mind the 
new Forest Suprex job concerning whicli 
no little roaring will emanate from the 
Jersey shores shortly. These boys also 
have a new screen in tow. More noise. 

The estimable Karl Brenkert, he of the 
lamp and effect-machine clan, dived into 
the projector field with a splash heard 
around the world by means of a new 
35 mm. theatre unit. Thus far the devel- 
opment has been the topic of much con- 
versation and scanty down-to-earth meaty 
data, the aforementioned sponsor being 
coy and playing hard-to-get, despite the 
fact that a dozen jobs have been spotted 
in widely separated locations. We'll get 
him — or else. There must be something 
tonic (who said "toxic"?) about these 
theatre projector waters, because the 
Holmes Co., of Chicago, which recently 
supplied RCA with a batch of 35 mm. 
jobs, is reported as having a tentative 
toe in the pool. 

Not to be outdone by mere manufac- 
turers, Larry (Essannay) Strong, a pro- 
jection mug from Chicago, pops up with 
Film-Weld, a unique film binder which 
is literally mopping up the field, and 
matches this with a new reel-end signal 
that touches neither reel nor film. A 
couple energetic Jerseyites, Heyer and 
Shultz by name, finally make good on 
the old promise to produce a practicable 
metal mirror — and selling them! The 
irrepressible Morrie (GoldE) Goldberg 
is chortling about Underwriters' approval 
for his new Micro-Matic enclosed rewind, 
and he exhibits boundless enthusiasm 
about a new oil-drive takeup. 

Ben Schlanger, the architect with 
a passion for proper theatre sight lines, 
is bent upon abolishing masking and let- 
ting the screen image light spray out 
over all sides of the picture sheet. 

Dr. A. N. Goldsmith has not yet con- 
structed a model of his completely auto- 
matic movie theatre, but we expect news 
of this thrust as soon as this eminent 
human technical encyclopedia finishes the 
job of masticating mentally his 97 tele- 
vision patents. 

AUGUST 1939 


NEW film emulsions are indispensable to 
motion picture progress, but only proved 
reliability and uniformity make them 
practicable. Eastman Plus-X, Super-XX, 
and Background-X have those priceless 
qualities — hence the everyday use they 
are enjoying throughout the industry. 
Eastman Kodak Company, Rochester, N. Y. 
(J. E. Brulatour, Inc., Distributors, Fort 
Lee, Chicago, Hollywood.) 



for general studio use for ait difficult shots 


for backgrounds and general exteriot work 





AUGUST 1939 

Film Projection by Discharge Lamps 

This communication from what is generally 
regarded as the outstanding technical research 
laboratory in the world treats with a subject 
of extreme interest to projectionists. The 
Philips organization, having pioneered in the 
development of the mercury vapor discharge 
lamp, is naturally interested in its progress — 
a fact which explains in part the unfavorable 

comment anent the carbon arc contained in 
the appended article. Elements other than 
the carbon arc in the projection process being 
"up to snuff," the carbon arc still remains 
the ideal light source and remains the means 
for the projection of extraordinarily fine 
screen images in thousands of theatres daily. 
— Editor. 

THE high intensity of illumination 
of the film which is necessary for 
kinema projection requires a very 
intense light source. It was therefore to 
be expected that the light source would 
be used for this purpose which had the 
greatest brightness known, namely the 
carbon arc. This light source, however, 
has various technical objections. The 
crater changes in shape and size and, 
moreover, tiny particles are thrown out 
of the arc which soon cause a decrease 
in the reflecting power of the condens- 
ing mirror. 

These objections have led to the at- 
tempt to replace the arc lamp by an 
electric filament lamp. With the increas- 
ing size of kinema theatres it was, how- 
ever, found impossible to satisfy the 
also increasing demands of the public 
as to brightness of the picture. It is 



therefore understandable that a light 
source has been sought with a greater 
surface brightness than a filament lamp 
and easier to operate than the usual 
carbon arc. 

Such a light source was discovered 
several years ago in the water-cooled 
mercury lamp, which easily matches the 
carbon arc and even the so-called "high- 
intensity" arc in brightness. This light 
source has none of the aforementioned 
disadvantages and has, moreover, the 
advantage of developing much less heat 
than the carbon arc. 

Because of the necessity of water cool- 
ing, and because of the linear form of 
the light source, new problems were pre- 

sented which made it necessary to con- 
sider anew the construction of the 
illumination objective. On the other hand, 
the small dimensions of the mercury 
lamp and its slight heat development 
offered new possibilities for the con- 
struction of the whole projector. These 
considerations have led to the construc- 
tion of an entirely new installation for 
film reproduction which makes full use 
of the advantages offered by the water- 
cooled mercury lamp. 

The most important data are given 
in Table A. 

• The Light Source 

The mercury lamp for film projection 
dissipates an energy of 1,000 W over 
a length of 12.5 mm. between the elec- 
trodes. It has an internal diameter of 
1.8 mm. and an external diameter of 4 
mm. The walls are of quartz and are 

AUGUST 1939 

Length of the discnarge 
Internal diameter 

12.5 mm. 
, 1 .8 mm. 

External diameter 

4 mm. 

Pressure of the mercury vapour 
p (mercury lamp 

ower j trans f ormer 4. rectifier 

100 Atm. 
1,000 W 
500 W 

2 A 

Working Voltage 

Ignition voltage 

Light flux 

Surface brightness , the axis of the discharge 


500 V 

800 V 
60,000 lm. 
57,000 c.p./ 

60 Im./W 

cooled with water. Two tungsten wires 
led in through the ends of the tube 
serve as electrodes. In addition to a 
small amount of mercury, the tube con- 
tains an inert gas filling of low pres- 
sure. This inert gas is necessary for 

For use in film projection the tube 
must be fed with direct current. A trans- 
former and a rectifier are used for this 

• The Optical System 

The requirements of the optical sys- 
tem for the projection of films and of 
lantern slides are to a certain extent 
opposite to each other. With films the 
film window is placed at the point where 
the beam emitted from the light source 
and concentrated by the condenser has 
the smallest diameter. In the projection 
of much larger lantern slides, the nar- 
rowest part of the beam is no longer 
chosen but on the contrary, exactly the 
place where the beam has its greatest 
diameter, i.e., immediately behind the 

The arrangement ordinarily used for 
lantern slides is much more satisfactory 
for mercury lamps, and actually forms 
the basis of the construction of the new 
installation for film reproduction. 

Figure 1 gives a cross-section and 
view from above of the optical system. 
The mercury lamp 1 is in a metal boat 
which is shown separately in Fig. 2. 
This boat is placed in a tube (see Fig. 
3) through which the cooling water 
flows. The boat is closed by a plane 
glass, 2. In front of this is a plano- 
convex lens, 3, which receives the light 


from the mercury lamp over an angle of 
divergence of about 90 degrees. 

This lens has a relatively small re- 
fraction because one surface is bounded 
by water instead of air. Therefore a 
second condenser lens, (4 in Fig. 2), 
must be used. Between the two lenses, 
3 and 4, space is left for the rotating 

The light which the lamp emits in the 
backward direction is directed forward 
by a cylindrical mirror, 5. It is desirable 
to concentrate as much light as possible 
in the neighborhood of the light source. 
A certain lateral deviation is, however, 
necessary because, due to the strong re- 
fraction of the quartz, it is impossible 
to send light through the free space be- 
tween the constricted discharge and the 
inner wall of the mercury tube. 

The action of the rear mirror may be 
seen in Fig. 4. If the path of the rays 
be examined in a transverse cross- 
section, four images are seen to appear 
beside the discharge, which together 
form a lighted surface about 8 mm. 
wide. In the longitudinal cross-section 
there is no focusing, but this is un- 
necessary because, due to the oblong 
form of the source, the beams have a 
sufficiently great angle of divergence in 
the longitudinal cross-section. 

The direct and reflected light of the 
mercury lamp must now be used to 
illuminate the film uniformly. A gradual 
variation of brightness, namely a decay 
of brightness towards the edges of the 
film, is by itself not a great objection, 
since the eye is also only slightly sensi- 
tive to differences in brightness. The 

eye is, however, very sensitive to small 
changes in the spectral composition of 
the light. Since the condenser is not 
completely achromatic, so that the light 
of the blue mercury line is distributed 
over the film in a somewhat different 
way from the green mercury line, very 
disturbing color differences might occur 
if there were a slight irregularity in 
the illumination of the film. 
• Light Production, Color 

When such differences in color are 
observed, it has been found sufficient to 
place a frosted glass plate between the 
source and the condenser. The spread- 
ing of the light by this plate is only 
slight, because it is immersed in water, 
i.e., in a medium with practically the 
same index of refraction. Nevertheless 
this scattering is enough to make the 
illumination of the film absolutely uni- 

The light flux which is directed on 


The tube which contains the boat for 
the mercury lamp. The boat is slid in 
from the right and fixed in position 
with a hollow screw in such a way that 
the flange forms a watertight closing. 
Afterward the large cover is set on the 
tube from the right. The electrical con- 
tact is first made through this cover 
between the positive terminal of the 
supply voltage and the pin of the boat. 
During assembly or demounting, there- 
fore, the lamp can never be under 

the screen is practically the same as 
that of a carbon arc of 45 amperes, and, 
with the sector rotating and without 
film, it is about 2,500 lumens. The light 
is bluish-white in color and resembles 
that of the so-called high-intensity arc. 
The spectrum of the light of the 
mercury lamp is, as is well known, not 

FIGURE 2. The boat with the mercury lamp. The num- 
bers give the chief dimensions in mm. The projecting 
pin on the right is one of the electrical connections, the 
other is formed by the container of the boat. The cooling- 
water flows in on the left and out through a hole in the 
rear wall. 

FIGURE 1. Cross-section of the optical sys- 
tem for the illumination of the film by 
means of a water-cooled mercury lamp. 1, 
mercury lamp; 2, glass plate; 3 and 4, lenses 
of the condenser; 5, rear mirror. 


Section (A) 
Light source 








7', 200 









Electric lamp 




5 4 





Carbon arc 
















11. 6 






1 1.1 





High-intensity arc 









High pressure mercury 
lamp for film projec- 









More highly loaded 
mercury lamp with 
red sector and yellow 









continuous but consists of a number of 
lines, chiefly a green one, a yellow one 
and several blue ones. However, thanks 
to the high pressure to which the mer- 
cury vapor is subjected, a continuous 
background appears between the lines, 
so that with increasing loading of the 
mercury lamp the spectrum begins more 
and more to resemble that of an in- 
candescent body. 

The spectral composition is of par- 
ticular importance when color films are 
shown. In that case it is not enough to 
require that the light source be "white," 
but the additional requirement must be 
made that the light must have about the 
same relative distribution in the various 
wave-length regions as daylight. 

In Table B the distribution is in- 
dicated of the light flux of the mercury 
lamps for kinema projection over dif- 
ferent sections of the wave-length scale, 
and compared with that of various other 
sources of white light. The choice of 
the sections is adapted to the properties 
of the eye. 

It may be seen from the table that 
the radiation of the mercury lamp is 
quite similar to that of daylight in the 
middle sections, 3 to 6. In the blue sec- 
tions, 1 and 2, the intensity is about 
twice as high. This excess of light can 
be absorbed by a yellow filter. The high- 
est relative deviations appear, however, 
in the red sections, 7 and 8, where the 

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Ir/v. y J 

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~%W? y^ 

The action ofthe rear mirror 


intensity of the mercury lamp is only 
one-half that of daylight. 

The intensity of the red radiation 
can be increased by using red-trans- 
mitting sectors instead of opaque ones 
on the rotating sector disc. A further 
increase of the intensity in the red is 
possible by increasing the specific load- 
ing of the mercury lamp. 

Experiments have shown that upon 
the application of these measures a satis- 
factory color reproduction is possible. 
The last line in Table B gives the spec- 
tral distribution of a mercury lamp with 
increased load provided with a red ro- 
tating sector and a yellow filter. 

The energy consumed by the mercury 
lamp (with rectifier) is 1.5 kw. In the 
case of a carbon arc of 45 amperes the 
total consumption is about 3 kw, so that 
a saving of 50 per cent is achieved. 
Because of this the heat development 
of the mercury arc is much less, and 
moreover about 90 per cent of the heat 
radiation is removed by the cooling 

# Arrangement of Installation 

Following the foregoing explanation 
of the optical system we shall consider 
the installation for film reproduction as 
a whole. Fig. 5 is a photograph of the 
apparatus. The compact structure, which 
was made possible by the very small 
dimensions of the light source, is im- 
mediately striking. 

The lamp forms, as it were, a unit 
with the film window. At the spot where 
the arc lamp ordinarily stands are the 
film drums. The arrangement has made 
it possible to mount one above the other 
the two projectors which are necessary 
in order to be able to change reels of 
film without interrupting the perform- 

ance. This means a great saving of 

In order to align the projectors in the 
vertical plane, they are mounted in a 
ring, as may be seen in the photograph, 
so that they can be turned about a 
horizontal axis. In the horizontal plane 
the projector cabinet which contains the 
ring can itself be turned a few degrees. 

In each of the projector cabinets there 
is the optical system with the necessary 
water-cooling, and further the scanning 
apparatus for the sound track with the 
first stage of the necessary amplifica- 
tion. In the cabinet also is the me- 
chanical arrangement for moving the 
film across the optical system and the 
sound head. In the cabinet below are 
the amplifiers and the supply apparatus. 

In the middle of either cabinet is the 
motor for moving the film. To the left 
of the motor the projection arrangement 
is mounted in a ring. Behind the motor 
are the two tubes which conduct the 


The Philips double film reproduction 
installation FP2. It consists of two 
projectors one above the other. The 
lower cabinet contains the amplifiers, the 
supply apparatus and the cabin loud- 
speaker. The two projectors are housed 
together with the necessary arrange- 
ments for sound scanning; behind each 
projector there are two film drums. 

cooling water to the jacket of the mer- 
cury lamp. The screened cable which 
connects the photocell for sound scan- 
ning to the photocell amplifier is in 
the upper left-hand corner of each pro- 
jection cabinet. 

Figure 6 gives pictures of several de- 
tails of the mechanism of the projector. 
The whole mechanism (mercury lamp 
and lenses) can be moved in a vertical 
direction (see A) by means of a knob. 
In this way the position of the film 
window can be so adjusted that in the 

AUGUST 19 3 9 

positions of rest of the rotating sector 
it corresponds exactly with the position 
of one film picture (framing). Another 
knob in the middle of Fig. 6 is that of 
a revolving head which contains two 
mercury lamps. By giving this knob a 
half turn the lamps can be interchanged. 
At the same time the connections for 
electric current and cooling water are 
switched over to the lamp put into use. 
The switching on takes place in four 

• Starting the Equipment 

1. Switching on of motor and pri- 
mary winding of transformer. 2. Motor 
brought up to normal number of revo- 
lutions. 3. Ignition of the lamp. 4. 
Current in lamp raised to normal work- 
ing strength. The lamp current can be 
read off from the ammeter. In the lower 
left-hand corner of Fig. 6 is the system 
for sound scanning. Below to the ex- 
treme left is the exciter lamp. Diagon- 
ally upward follow: a condenser, a slit, 

Front side of projector 

a reversed microscope lens which focuses 
a reduced image of the slit on the 
sound track, and a photocell contained 
in the grey box. 

On the cover of the upper projector 
cabinet the arrangement for projecting 
lantern slides is mounted. It consists of 
two mercury light sources, each with 
its condenser and projection lens. The 
two systems work alternately. Upon 
changing from one slide to another the 
beam of light of one system is gradu- 
ally cut off by a lever switch with the 
help of a diaphragm set up behind each 
objective, while at the same time the 
beam of the other system is raised to 
full strength. 


The organized studio projectionists are 
not in the least secretive about the fact 
that they now have their own unit in the 
I. A.— Local 165 — and have established 
headquarters at 708 North LaBrea Ave., 
Los Angeles. A membership of 272 studio 
men (the "economic royalists" of the pro- 
jection craft) are enthusiastic about their 
new baby and feel that they provide the 
nucleus for a very successful Local. 

S.M.P.E. Projection Practice, Exchange 
Committees Report Progress 

Appended hereto are the current reports by the Projection Practice and Ex- 
change Practice committees of the S.M.P.E. The former group has several im- 
portant projects under way, including an investigation of screen brightness and 
means for measuring it, and an inquiry into sources of theatre power supply. 
The Exchange group is primarily interested in improving methods of handling 
prints, particularly in theatre projection rooms. 


A NUMBER of important matters are 
before the Committee at this time. 
As detailed information on these mat- 
ters is not yet complete, they will be 
reported on more fully at a later date. 
Among these projects are: 

(1) Study of screen brightness and 
methods of measuring it. 

(2) Problem of obtaining simple 
and practicable meters for measuring 
screen illumination and brightness. 

(3) Study of screen sizes and 
placement, and seating arrangement. 

(4) Study of tolerances and ten- 
sions permissible in motion picture 
projection equipment and means of 
measuring and checking the values. 

(5) Revision of the NFPA Regula- 
tions for Handling Nitrocellulose Mo- 
tion Picture Film. 

(6) Survey of the power require- 
ments of motion picture theatres. 

• Screen Brightness 

The Committee has had under con- 
sideration for quite some time the sub- 
ject of measuring reflected light, and 
while it is relatively easy to obtain 
meters which are calibrated correctly 
on diffused light, the readings obtained 
from motion picture screens are greatly 
influenced by the fact that all com- 
mercial screens are in some degree 
specular, that is, not completely dif- 
fusing. This fact precludes the possi- 
bility of easily making absolute bright- 
ness measurements, and for this rea- 
son the Committee is having tests made 
on various types of screens to deter- 
mine whether an empirical method of 
testing can be established and whether 
thereafter it can be systematically cor- 
related to a primary and precision 
method yet to be devised. 

The report of the Committee, pub- 
lished in the November, 1938 Journal 1 , 
contained the complete recommenda- 
tions of the Committee with regard 
to the National Fire Protective Asso- 
ciation Regulations for Handling Nitro- 
cellulose Film. These proposals were 
submitted to the NFPA and are now 
being considered by their Committee 
on Hazardous Chemicals and Explosives. 
It is expected that final action on 

this revision will be taken at the May 
convention of the NFPA at Chicago.* 
The Committee feels gratified that 
a great number of its proposals have 
been accepted by the NFPA Commit- 
tee without modification. As it has 
been many years since the last issue 
of the "Regulations," this revision ful- 
fills an important need of the indus- 
try in bringing theatres up-to-date as 
regards equipment and installation. 

• Power Requirement Survey 

A great deal has been written in 
various non-technical trade publications 
on the subject of theatre lighting and 
power equipment operating characteris- 
tics. Also, many attempts have been 
made to relate the lighting and power 
equipment installation to total energy 
costs. Developments in the motion 
picture field have reached the stage 
where every important operation is re- 
lated in some manner to electrical ap 
paratus of widely varying types. 

Some exhibitors and projectionists 
do not have reliable sources of in- 
formation to determine whether or not 
their equipment and their methods of 
operation conform to present-day trends. 
There has long been a need for a 
comprehensive report showing the vari- 
ous types of electrical equipment, their 
load characteristics, and their use and 
cost of operation. The Committee 
now has in progress the preparation 
of such a report. 


During the past year meetings were 
held regularly each month. Although 
there is little material of a specific 
nature to be reported at this time, 
these meetings have proved of great 
value in providing periodic contacts 
among 'the heads of exchanges of the 
various companies, and to permit inter- 
change of ideas and discussions of 
technic, administration and conduct, to 
the general betterment of exchange 

Some of the studies initiated last 
year have not yet been completed. For 
(Continued on page 25) 

^.P. for Nov., 1938, p. 12. 

*NOTE: These proposals were approved without 

important modification, by the NFPA at its 

recent Convention, as reported in I. P. for May, 

1939, p. 15 ("Many Important Changes in 

NFPA Projection Room Regulations")- 



The Fundamentals of Mathematics 



///. Multiplication, Division, and Factoring of Polynomials; 
Ratio and Proportion. 

It will be a help if the reader digest each article as it appears, 
for the ideas presented in subsequent sections hinge upon an under- 
standing of topics discussed in earlier sections. Further, it is desir- 
able that the issues of this series be cached away after reading, as 
back-reference may be\ useful before the series is completed. 

The various examples given throughout the series will be best 
understood if the reader will work them out on paper, duplicating, 
step-by-step, the solutions given in the text. 

IN the second section of this series 
some multiplication was undertaken 
with the purpose of showing how to 
handle positive and negative signs, and 
how to perform the multiplication opera- 
tion upon monomials. A monomial, as 
we have seen, is a single algebraic term 
which is composed of a coefficient and 
one or more letter factors. Thus la, 
— 26, \6x-y, Iz, are monomials. 

It is our purpose now to extend our 
ideas on multiplication so that we can 
multiply algebraic quantities made up ol 
several terms — that is, polynomials. A 
polynomial is merely a group of mon- 
omials separated one from the other by 
the signs of addition or subtraction. Thus 

7a— 2b+16x 2 +7z, and 
4ac+3bc+9c 2 

are polynomials. 

Let us consider first multiplication of a 
polynomial by a monomial. Multiply 
each term of the polynomial by ihe mon- 
omial, and add together the individual 
products with due regard to sign. 

Find the product of 8c 2 + 4s — 9t 2 and 

8c 2 +4s— 9t 2 


16c 3 +8sc— 18t 2 c 
Find the product of — 6x+9d 2 — 4 and 

— 6x+9d 2 — 4 

— 18xs+27d 2 s— 12s 

From this point it is a short jump to 
multiplication of a polynomial by a poly- 
nomial. Multiply each term of the first 
polynomial by each term of the second 

polynomial, and add together the indi- 
vidual products with due regard to sign. 
Find the product of 4a — 4b and 3a — 

4a — 4b 

3a— 3b 

6k +4t +3m 
4k +4s —2m 

— 12km— 8tm— 6m 2 
+ 24sk+16st+12sm 
24k 2 + 16kt +12km 

24k 2 +16kt+24sk+16st+12sm+ — 8tm— £m 2 

Division of polynomials is next on the 
program. As a starter, let us center our 
attention first upon division of a poly- 
nomial by a monomial. Divide each term 
in the polynomial by. the monomial, and 
add the individual quotients with due re- 
gard to sign. 

Find the quotient of 

4x 3 + 6x 2 + 8x 4 

— 12ab+12b" 
12a 2 — 12ab 

12a 2 — 24ab+12b 2 

Find the product of 7x — 4y and 3x+ 

7x— 4y 

+ 42xy— 24y 2 
21x 2 — 12xy 

21x 2 + 30xy— 24y 2 

Whenever, in multiplication of poly- 
nomial by polynomial, some individual 
products are similar terms, the similar 
terms are placed in a column for con- 
venience in adding, as we have done 
above. But when similar terms are not 
formed, as in the appended example, the 
terms are not placed in columns. 

Find the product of 7sx — 3y and 2m + 

7sx — 3y 

+ 28sxt— 12yt 

14sxm — 6ym 

14sxm— 6ym+ 28sxt— 12yt 

Thus far our examples have been poly- 
nomials of two terms. Herewith is an 
example of multiplication of two poly- 
nomials, each of which is composed of 
three terms. 


4x 3 +6x 2 + 8x 4 4x 3 6x 2 8x 4 

= — + — + — 

2x 2x 2x 2x 

= 2x 2 + 3x+4x 3 

Hence we split a problem of this type 
up into several divisions, each of which 
is a monomial divided by a monomial, 
and in that form the problem is easily 

The permissibility of changing the 
form as we have done above is easily 
justified by a numerical example, thus: 

4+2+6 12 
2 2 

4 2 6 

2 2 2 

Here's another example for this 
method : 

6m 2 x 4 — 8mx 3 + 4m 2 x 2 

6m 2 x 4 8mx 3 4m 2 x 2 

■ + 

2mx 2mx 2mx 

3mx 3 — 4x 2 +2mx 

The next step forward is consideration 
of division of a polynomial by a poly- 
nomial. We will use as an illustrative 
problem : 

7xy+3y 2 +2x 2 -=-y+2x 

First we rearrange the dividend and 
divisor, so that they are in ascending or 
descending powers of some letter which 
exists in both. When we rearrange a poly- 

AUGUST 1939 


nomial in ascending powers of some 
letter, say x, we mean that the terms are 
re-grouped so that the term containing 
the lowest power of x is written first, the 
term containing the next larger power of 
x is written following, and so on. When 
we rearrange a polynomial in descending 
powers of some letter, say x, we mean 
that the terms are re-grouped so that the 
term containing the largest power of x 
is written first, the term containing the 
next smaller power of x is written fol- 
lowing, and so on. 

Hence, our dividend in descending 
powers of x is: 

2x 2 + 7xy+3y 2 

And our divisor in descending powers 
of x is : 

2x + y 

Place the rearranged dividend and 
divisor in the form used in arithmetical 
long division : 

2x+y | 2x 2 + 7xy + i5y 2 

Divide the first term in the dividend 
(i.e., 2x 2 ) by the first term in the divisor, 
(i.e., 2x) . Write the result as the first 
term in the quotient: 


2x+y |2x 2 + 7xy + 3y 2 

Multiply all terms of the divisor by the 
first term in the quotient: 

2x+y | 2x 2 + 7xy+3y 2 
2x 2 + xy 

Subtract the product: 

2x + y j2x 2 + 7xy+3y 2 
2x 2 + xy 


Form a new dividend with the re- 


2x+y ]2x 2 + 7xy+3y 2 
2x 2 + xy 

6xy+3y 2 

Proceed as before, that is, divide the 
first term in the new dividend (i.e., 6xy) 
by the first term in the divisor, and place 
the result in the quotient. The result is 
then the second term in the quotient. 
Multiply all terms of the divisor by this 
second term in the quotient: 

x + 3y 

2x + y 

2x 2 + 7xy + 3y 2 
2x 2 + xy 

6xy + 3y 2 
6xy + 3y 2 

We chose the dividend and divisor in 
the foregoing problem so that the divi- 

dend was exactly divisible by the divisor. 
That is, there was no final remainder. 
Appended is another case wherein exact 
division is not possible. The quotient 
in this instance turns out to be a poly- 
nomial and a polynomial fraction: 

2k + 4s 

4k+s|8k 2 +20ks+14s 2 
8k 2 + 2ks 

18ks+14s 2 
16ks+ 4s 2 

2ks+10s 2 

2ks+10s 2 



The above example is similar to an 
arithmetical problem in long division 
wherein exact division is not possible, 
like this: 

43 [973 



27 27 

.'.Quotient = 22 -| , or, simply, 22 — 

43 43 

We take leave of division to center our 
attention on the next topic, factors. We 
found in Section I of this series that 
when a product is formed by multiplying 
together individual numbers, the indi- 
vidual numbers are factors of the prod- 
uct, and further, that multiplied combin- 
ations of the individual numbers are fac- 
tors of the product. That preliminary 
discussion, however, was confined to 
monomials. It was shown, as an ex- 
ample, that the factors of the monomial 
5cd are 5, c, d, 5c, cd, 5d. Polynomials 
may also be factored, in some instances. 
Factoring is often useful when dealing 
with polynomial fractional expressions 
such as 

5c— 5d 

5x — 5y 

for through factoring such expressions 
may be simplified. The factor common to 
the numerator and the denominator of a 

fraction such as we use for illustration 
may be found, then cancelled above and 
below, thereby finally producing a simp- 
ler expression. 

From inspection we can factor 5c — 5d 

5c— 5d=5(c— d) 

From inspection we can factor 5x — 5y 

5x — 5y = 5 ( x — y ) 
Therefore : 

5c — 5d 5(c — d) c — d 

5x — 5y 5 (x — y) x — y 

In some examples of this nature factor- 
ing so simplifies the expression that the 
denominator becomes simply unity, and 
thus need not be written in the simplified 
expression. For example, factor and 
simplify : 

4y 2 + 8y+10zy 


From inspection it is found that each 
term in the numerator is evenly divisible 
by 2y. Hence 2y is a factor of the num- 
erator. Therefore : 

4y 2 + 8y+10zy 2y(2y+4+5z) 

2y 2y 


Sometimes proper re-grouping of the 
terms in a polynomial will help in the 
factoring. Take, for instance, the poly- 
nomial expression: 

am + bn + an+bm 

Re-group this expression so that all 
the terms containing a are in one group, 
and all the terms containing b are in one 

am+bn + an + bm= 
(am+an) + (bm+bn) 

In the first group, a can be placed out- 
side the parenthesis as a factor; in the 
second group, b can be placed outside 
the parenthesis as a factor: 

am+bn+an + bm=: 
a(m+n) +b(m+h) 

It is seen that the polynomial (m+n) 
is common to both groups in their new- 
form above. The polynomial (m+n) is, 
therefore, a common factor of the groups, 
and when we factor out (m+n) from the 

Clinical Note For Theatre Managers 

"Even under adequate lighting and with normal vision, it has 
been estimated that there is a consumption of a quarter of the 
bodily energy in the process of seeing. When vision is normal, 
the ease of seeing is controlled almost entirely by sufficient and 
proper lighting. However, when the illumination is improper 
or inadequate, and when the vision is poor, then consumption 
of bodily energy is increased above the usual amount." 

Dr. Charles Sheard, The Mayo Foundation 



groups we get the following expression: 

am+bn + an + bm= (m+n) (a+b) 

Thus our factors of am + bn + an+bm 
are (m + n) and (a+b), for if these 
polynomials are multiplied together the 
product will be the original expression, 
am + bn + an + bm. The entire proceed- 
ure for this example just completed may 
be clarified if we substitute numbers for 
the symbols. In 

am + bn + an + bm 

substitute a = 2, 6 = 3, m — 4, n=5 

(2X4+2X5) + (3X4+3X5) = 

2(4+5) +3(4+5) = 
(4+5) (2+3) = (9) (5) =45 

Often polynomials can be immediately 
resolved into factors through recognition 
of the polynomial as a power or a prod- 
uct of lesser polynomials. 

Since a+b 2 = a 2 + 2ab+b 2 , the factors 
of a 2 +2ab + b 2 are (a+b) and (a+b). 

Since (a— £,) 2 = a 2 — 2a\b+b 2 , the fac- 
tors of a 2 — 2ab + b 2 are (a — b) and 

Since (a+b) (a — t) =a 2 — b 2 , the fac- 
tors of a 2 — b 2 are (a+b) and (a — b). 

In consequence, if we have a fraction 
such as 

a 2 +2ab+b 2 

a 2 — b 2 

which at first glance looks a little in- 
volved, through factoring we can readily 
boil it down to a very simple expression : 

a 2 + 2ab+b 2 (a+b) 2 

-b 2 

(a+b) (a-b) 

(a+b) (a+b) a + b 

(a + b) (a— b) a— b 
Ratio and proportion are the final 
items to study in .this section of the 

When we seek the relative magnitude of 
a number x compared with a number y, 
we divide x by y. In other words, when 
we desire the ratio of x to y, we indicate 
the operation to be performed in any one 
of the following equivalent forms: 
— x/y xH-y x:y 


The last form is frequently used when 
we are thinking particularly of a ratio 
rather than of a mere division. Per- 
sonally I prefer writing the ratio of x 

to y as simply — , for it tells the story, 


and avoids introduction of a more or 
less superfluous member to our family of 
operational symbols. 

What is the width ratio of 35 mm film 
to 16 mm film? 


Width ratio= — =2.18 approx. 


In this example the ratio is approxi- 
mate because 35 is not exactly divisible 
by 16. But the more decimal places 
found for the ratio, the more accurate is 
the ratio. And any degree of accuracy 
is obtainable by simply carrying the 
division far enough. 

When we speak of the ratio of two 
magnitudes it is obvious that the magni- 
tudes under consideration must be the 
same kind of thing. It would be an 
absurdity, of course, to seek the ratio of 
the number of feet of film on a reel to 
the seating capacity of a theatre. But 
it conceivably could be useful, however, 
to know the ratio of the footage on one 
reel to the footage on another reel, for 
that ratio would give us an idea of the 
relative running time of the respective 

Certain things about ratios are useful 
to know. 

The value of a ratio is not changed if 
both terms are multiplied by the same 
number, for: 

a na 

b nb 

The value of a ratio is not changed if 
both terms are divided by the same num- 
ber, for: 

b b nb 

A given number cannot be added to or 
subtracted from the terms of a ratio and 
keep ithe ratio value unchanged. 

a a+n 

b b+n 

a a — n 


b b— n 

Ratios are used in forming proportions. 
An equation comprised of two equivalent 
ratios is called a proportion. Thus the 

a c 

is a proportion. It is read: a is to b as c 
is to d. 

In this general expression for a pro- 
portion the terms b and c are called 
means, and the terms a and d are called 
extremes. Various useful things to know 

about proportion are stated and proven 

// two ratios form a proportion, the 
product of the means is equal to the 
product of the extremes. 
Given : 

a c 

Cross-multiply to clear of denominators: 

da = cb 

// the product of two numbers is equal 
<to the product of two other numbers, a 
proportion can be formed of the numbers 
by setting one pair as means, the other 
pair as extremes. 
Given : 

This is the same as: 

da cb 

1 1 
Cross multiply: 

a cb a c 

1 d b d 

// two ratios form a proportion, inc. 
terms inverted are also in proportion. 
Given : 

a c a c 

b d b d 

1 1 b d 

a c a c 

// all terms of a proportion are raised 
to a given power, the terms still are in 
Given : 

a c 

GH:) : 


Here's a practical problem to wind up 
this section. If it requires 10 minutes to 
run 900 feet of film through a projector, 
find by proportion the time required, t, 
to run 720 feet. By proportion, 900 is to 
720 as 10 is to t: 

900 10 

720 t 

Solving for t: 

(900) (t) 


(10) (720) 


^8 minutes. 


AUGUST 193 9 


The H-S All-Metal Arc Reflector 

PROBABLY the foremost thought 
in the minds of projectionists 
using metal reflectors is the inher- 
ent element of rugged dependability so 
evident in a piece of solid metal, from 
which this type of unit is fabricated. 
While this is an indisputable advantage, 
it is only one of the many basic poten- 
tiahties of a unit constructed expressly 
for use in high-intensity projection 
where extreme temperature must be 
contended with constantly. 

The three outstanding reasons for 
rapidly increasing use of metal re- 
flectors are that they are unbreakable, 
and are not subject to pitting and 
tarnishing. These advantages not only 
lead to definite economy but assure 
continuous maximum performance. Re- 
sistance to tarnishing and pitting is 
accomplished by the utilization of a 
metal known as rhodium possessing 
characteristics which make it exception- 
ally suitable for use in projection 
mirrors. The unique metal has a melt- 
ing point of about 3,600° F, or almost 
1,000° above the melting point of steel. 
In solid form it is insoluble in any 
single acid, thus giving it immunity to 

• Efficiency, Ease of Cleaning 

The hardness of this metal is im- 
portant as it determines resistance to 
scratching. It is of interest to note 
that rhodium has a Rockwell hardness 
of 90 as compared with that of tool 
steel at 60. The question ot scratch- 
ing is of paramount importance to pro- 
jectionists, as carbon particles and other 
foreign matter are sure to work into 
the cleaning process of any projection 
reflector. Representative tests have been 
made to determine the percentage of 
loss suffered in this manner. A new 
metal reflector was given a photometric 
recording through a standard projection 
system, removed and scoured with sand 
until the entire surface was covered 
with scratches. This extreme test pro- 
duced a loss of reflectivity of only 4 
per cent, which leads to the conclusion 
that average scratching, even over an 
extended period of years from normal 
cleaning, would result in a negligible 
light loss. 

The projectionist will welcome the 
fact that these new mirrors may be 
cleaned while hot with a wet cloth 
without damaging them in any way, 
and. if he so desires, he may remove 



The utilization of all-metal reflector mir- 
rors for motion picture projection work 
has long been the goal of several 
earnest experimenters, and the topic 
of much discussion among projection- 
ists. Current extensive promotional 
work in behalf of this type of mirror 
in the theatre field warrants the at- 
tention of projectionists to the end 
that they may be familiar with the 
characteristics of this new projection 

the reflector and douse it in cold water 
without damaging its curve or its shape. 
As no accumulations of particles from 
the arc occur, these reflectors may be 
cleaned easily at any time during their 
life. No special and expensive cleaners 
are needed for this operation, as pow- 
dered Bon Ami, an excellent agent for 
the purpose, is supplied free of charge 
by the manufacturer. 

These reflectors, unlike some previous 
metal mirrors, need never be returned 
to the factory for repolishing, the finish 
being permanent. Exhaustive tests have 
been conducted on these units with 
high-intensity arc sources for the past 
five years, the present units having 
been designed on the findings of this 
extensive research, which has been 
based largely on the suggestions and 
criticisms of the projectionists in whose 
hands these mirrors have been placed. 

• Reflectivity, Color Response 

An interesting fact concerning mirrors 
of this design is their ability to retain 
heat. After being heated by the first 
few minutes of projection they will hold 
their temperature throughout the day, 
thus minimizing expansion and contrac- 
tion. No change in curve or focus 
occurs, even when utilized with the 
most powerful type arcs operating at 
extreme angles of projection, the heat 
flowing evenly through the highly con- 
ductive metal of which they are com- 

The reflectivity of rhodium has been 
placed at 77 per cent by reliable 
sources, and the spectral response char- 

acteristic of this metal represents ex- 
cellent fidelity throughout the visible 
spectrum. This fact alone, however, 
does not tend to produce a color-free 
system which will faithfully reproduce 
the snow-white characteristics of the 
crater of simplified high-intensity type 
carbons. The final step is accomplished 
through precision of curvature, any 
deviation from which results in the 
majority of unwanted color. 

Relative to the correction of curve, 
three important factors warrant con- 
sideration: (a) color rendition (b) 
working range and (c) distribution. 
Foreign color differing from that of the 
crater appears in the following manner: 
let us suppose we are imaging the 
crater of a simplified high-intensity type 
source, as shown in Fig. 1, in which 
the colors of the arc are divided into 
three zones marked C, A and B. The 
first section C represents the discharged 
gases of blue and purple color. Sec- 
tion A represents the snow-white area 
formed in and directly adjacent to the 
crater floor of the arc. Section B 
represents an area formed by the glow- 
ing carbon surrounding the crater which 
is yellowish in color. 

To produce a snow-white image focus- 
ing of zone A must be accomplished 
individually without including zones B 
and C and their undesirable color char- 
acteristics. This condition of separa- 
tion of the zones can only be accom- 
plished by the utilization of a highly 
accurate ellipsoidal curvature as nearly 
free from spherical aberration as pos- 
sible, which must be a first-surface 
mirror of a material of undistorted 
spectral response. 

Figure 2 represents resulting color 
imaging due to incorrection of curva- 
ture from spherical aberration. E rep- 
resents incorrection of curve in which 
the reflecting surface is shown forward 
of the true ellipsoidal curve; while F 





represents a reverse condition, the re- 
flecting surface being behind the true 
ellipsoidal at this point. 

Following the incident light reflected 
from the white section of the arc, we 


The projectionist will find it possible 
to produce improved results as the 
range of focal change is greatly in- 
creased, that is, the positive carbon 
may "wander" ahead or behind its set- 

all parts of the reflecting surface to 
focus at a single point. Poor distribu- 
tion may be brought about by: (1) 
unmatched reflector and lens speed (2) 
misalignment and (3) improper work- 




find that in case E the white light 
does not come to conjugate focus at 
the aperture but crosses the axis some- 
what further on (N in Fig. 2) ; and in 
case F the reverse holds true as the 
conjugate focus from the white section 
occurs on the axis before reaching the 
aperture (M in Fig. 2).. 

. Let us suppose that this incorrection 
produced a condition that would cause 

(in E) an imaging at conjugate focus 
of the yellow area shown in Fig. 1, 
and that in like manner (at F) the 
blue area would also be focused at 
the aperture but the white section 
would not individually cross the axis 
at the aperture. In this way either of 
the undesirable colors might be focused 
individually or both might fall at con- 
jugate focus at the same point produc- 
ing blue or yellow or a mixture, re- 
sulting in a greenish tint. 

As all pencils of incident light from 
a corrected curve fall at conjugate focus 
at one position on the axis, as shown 
in Fig. 3, the color zones on either 
side of the white section A fall at con- 
jugate focus at relative points on the 
axis behind and in front of the aper- 
ture, thus producing accurate imag- 
ing of section A individually, so de- 
sirable in obtaining white light. 

• Individual Equipment Test 

As the new H-S metal mirrors are 
corrected for this condition, they are 
particularly suited for the projection of 
color motion pictures, in which snow- 
white illumination is an absolute neces- 
sity if maximum results are to be 
obtained. Black-and-white projection is 
also improved in depth as well as defi- 
nition, as a crispness of high lights, 
through added contrast, becomes evi- 

ting to a much greater distance before 
the screen image becomes yellow or 
blue. So that the projectionist may 
conduct an accurate test on his own 
equipment, the following method is 

Punch a pin-hole in a piece of thin 
metal in such a manner that it may 
be placed over the aperture with the 
hole exactly centered. Operate the pro- 
jector without film, and with a piece 
of cardboard find the position in front 
of the objective lens where an image 
of the reflector will appear in focus — 
this is, such as point Y shown in Fig. 
4, representing image formation. (X 
represents the aperture position.) 

When the correct focus is located a 
H-S metal reflector will produce a clear 
white disc of light at point Y. If the 
focal distance be lengthened, areas of 
blue and purple will appear, and by 
shortening the focal distance, yellow 
and brown areas will be noted. Uncor- 
rected reflectors produce color at all 
settings and it is impossible to obtain 
a clear white disc. 

This simple test may also be utilized 
in setting up indicator cards accurately 
or being certain of perfect focus when 
inserting a new reflector. 

It is evident from this test that- an 
uncorrected reflector which is never free 
from color has no range, as the slightest 
focal change will immediately amplify 
either the blue into purple or the yel- 
low into brown; while the corrected 
unit producing a clear white disc must 
move some distance before any color 
will appear, and still further before 
the deeper hues are evident. 

Distribution of screen illumination is 
improved through corrected curve, as 
spherical aberration is reduced bringing 


X Y 



ing distance. An uncorrected mirror is 
always at an improper working distance 
at some part of its curve, usually at 
the outer part, as this is the most 
difficult to make accurate. 

For example, let us suppose that in 
testing as described, we find that an 
uncorrected mirror produces a ring of 
purple and blue around the outer por- 
tion when focused to an optimum set- 
ting. We know that this color denotes 
a long focal length, although the rest 
of the mirror is functioning properly. 

As every part of an ellipsoidal curve 
will throw a complete "spot," we know 
that the complete image of the crater 
thrown on the aperture is composed of 
an infinite number of superimposed 
"spots" each one progressively smaller 
as reflected respectively from center 
to outer parts of an ellipsoid, thus 
the outer areas form the small- 
est of these discs and produce the 
bright center of the screen image. If 
the test shows these areas to be long 
in focus, they are then producing even 
smaller discs and brighter central zones. 

In a corrected reflector the smallest 
disc is ample in size to cover the 
aperture, and all other superimposed 
discs focused at the same point form 
a solid area of well-distributed light 
at the conjugate focus. 

The correction of H-S metal mirrors 
also assures very close standardization 
in focus and efficiency, making possible 
their use interchangeably. 


The "/" number engraved upon the 
lens mount simply indicates the relation- 
ship between the focal length of the 
lens and the diameter of the largest stop. 
For example, "//2" with a lens of 2-inch 
focal length will indicate an effective 
aperture of 1 inch. Light loss through 
reflection within the lens is not taken into 
account in this calculation. 

In every optical combination light loss 
appears, owing to reflection from each 
glass to air surface. The smaller the 
number of glass-to-air surfaces the lens 
has, the greater is the freedom from re- 
flection and consequent light losses. 

Don't say "film cement"— Say "FILM-WELD," 
the modern film bind that never thickens, 
SCREEN spoils or discolors, firmly binds all film, and 
goes twice as far as cement. — adv. 

AUGUST 1939 


Process Projection Specifications 



Normal-Speed Head 

APERTURE (Basic): 

The projector head shall be so de- 
signed that an F1.6 cone of light can 
be accommodated through the aperture 
and fill an F1.6 projection lens from 
all parts of the picture, necessitating 
that the opening behind the aperture 
be of sufficient angle to allow the 
above cones of light to reach all parts 
of the aperture. The projector head 
should be designed to accommodate 
F1.6 lenses (when such fast lenses are 
satisfactorily developed) and permit 
lenses of large diameter* to come close 
enough to the aperture and not inter- 
fere with the operation or steadiness 
of the movement to obtain a proper 
focus on any length of set-up. A 
full screen aperture, 0.950" by 0.723", 
shall be provided. 


The projector head should be de- 
signed for a maximum shutter open- 
ing of 240°, this to mean that the 
film shall be at rest and the shutter 
to fully clear the aperture for this 
period of time.f 


A readily accessible synchronizing 
device which is quick and positive in 
operation shall be incorporated in this 
design. This device shall synchronize 
the projector and camera shutters to 
a tolerance of ±2°. 

Provision shall be made in the de- 
sign of the projector head motor 
drive so that the projector can be 
inter-locked with the camera and . re- 
corder motor drive system, and so 
that it will maintain the tolerances as 
given above under the basic recom- 
mendation "Synchronizing". 


A cooling device shall be provided 
in the optical system or incorporated 
in the aperture design. It has been 
suggested that a stream of air striking 
the film from the projection lens side 
and away from the light source, be 
employed. Such a device, if within 
the specifications given under "Noise 
Level," would also help to meet the 
recommendations given under "Posi- 
tion of the Film During Exposure," 
as a means of holding the film in the 
aperture during exposure. 

For the mirror or straight condenser 
type of lamphouse, the design shall 
also include a means, located between 
the gate and light source, to eliminate 
from the film aperture assembly that 

"NOTE: See "Standards of Lens Mount 

tNOTE: It is understood that all equipments 
shall be equipped with rear shutters. 7t has been 
further suggested that a 240° shutter be de- 
veloped for the camera. 

portion of spill light not actually used 
in the aperture. This device should 
be interchangeable to accept an F1.6 
to F2.3 cone of light. The develop- 
ment of such means or device is 
recommended primarily to decrease 
the amount of heat on the film trap 
assembly with no loss of light in an 
F1.6 system. 

In the relay system such a device 
may not be necessary as the amount 
of spilled light is practically nil. 
However, provision should be made 
for such a device should it be found 

PINS (Basic): 

Inasmuch as steadiness of picture 
is the basic and primary requisite of 
a background projector equipment, the 
design shall be such as to include 
pilot pins providing rock-steady regis- 
tration. These pilot pins may be either 
moving or stationary, providing the 
above specified registration is obtained 
and the pins stand up reasonably well 
under projection conditions.* 

TRATION (Basic): 

Adjustment control means shall be 
provided in registration to accom- 
modate a maximum film shrinkage of 
0.030" per foot, this adjustment to 
be calibrated against the vertical ad- 
justment of the aperture. 


(Accessorv) : 

// possible, means should be provided to 
reverse the reeistering pilot pins to give 
good registration to a background vrint 
when it is necessary to turn the back- 
ground print over for projection purposes. 


Sufficient clearance, that is, space 

*N0TE: The pilot pins of the projector should 
engage the same perforations as the camera and 

Classifications in Report 

In order to clearly specify the relative 
importance of the various recommenda- 
tions included in the report, each sub- 
heading in each part is indicated by one 
of the three following classifications: 

BASIC — Recommendations so in- 
dicated incorporate definite require- 
ments and principles. (Printed in 
bold face type.) 

AUXILIARY — Recommendations so 
indicated are suggested methods of meet- 
ing basic requirements. (Printed in 
light face type.) 

ACCESSORY — Indicates optional spe- 
cial refinements which add to the ease 
of operation of equipment. (Printed in 
italic type.) 

between the aperture and lens, shall 
be left in the design to accommodate 
a projector head giving the steadiness 
required in the above specifications. 
(See "Aperture".) 

MOVEMENT ^Basjc) : 

The projector iiean shall be so de- 
signed as to have tne amlity to run 
either forward or backward with per- 
fect registration with a take-up de- 
signed to take care of this two-way 
operation. This should be accom- 
plished with no damage to the film 
as specified under "Operating Speed 
of Head". This type of two-directional 
projector head also fulfills the func- 
tion of projecting a back-cranked 
scene with the camera running forward 
and the projector running backward, 
both shutters operating in synchron- 

This recommendation is made after 
consideration of observations and com- 
ments made by those members of the 
Committee who have worked with 
this type of equipment. The result- 
ant saving of production time will 
far more than offset any added diffi- 
culties encountered in securing such 

(Accessory) : It has been suggested 
that the design of the two directional 
movement be such that the background 
print can . be rewound without taking the 
film from the projector head, by disengag- 
ing the synchronous motor from the dis- 
tributor and operating independently. 

POSURE (Auxiliary): 

A method is desired in the design 
which will aid in holding the film as 
near as possible in the same exact plane 
during each exposure period under any 
heating or operating condition. (See 
"Cooling Device.") 

ROTATION OF HEAD (Accessory): 

The projector head should be so de- 
signed as to rate 90° either to the right 
or left about the optical axis, making a 
total circular coverage of 180° 

(Accessory) : It has been suggested that 
for the purposes of rigidity and registra- 
tion in the equipment an attachment or 
device be designed to rotate the projected 
image 90° to the right or to the left, mak- 
ing a total circular coverage of 180°, 
rather than rotate the projector head. 
This might be accomplished through the 
use of prisms, first surface mirrors, or 
adaptor plates used in conjunction with 
a separate head. 


The design shall include a remote 
control for focusing, operating from 
the camera position. 

(Auxiliary) : It has been suggested that 
the above * focusing control be provided 
with a rheostat and be operated by a 

(Continued on page 23) 



Industry Ills Many and Serious 

IT SEEMS pertinent at this time to 
consider the turn of events within the 
motion picture industry which, al- 
though non-technical in character, are 
of such importance as to relegate tele- 
vision to the level of a minor industry 
worry (only a few weeks ago television 
jitters were very conspicuous on all 
sides) and affect profoundly the welfare 
of everybody engaged in motion picture 
work — including projectionists. 

The industry's cup of woe apparently 
was filled to the brim what with a run 
of poor product and consequently sharply 
reduced theatre takes, estimated to ap- 
proximate 40 per cent in a majority of 
situations; with Hollywood sticking pig- 
headedly to fantastic picture budgets for 
product most of which couldn't and 
didn't draw flies to theatre box-offices, 
and with Uncle Sam's anti-trust suit 
against every major industry rocking the 
industry to its already well-rounded 
heels. But this was as nothing compared 
with what was in store for this madcap 
merchandiser of glamour, as witness the 
following developments: 

• List of Stupidities 

1. Passage in the House of Represen- 
tatives of the Neely Bill (with favorable 
Senate action forecast), providing for the 
elimination of block booking and the in- 
stitution of various other "ethical" and 
"equitable" trade practices designed to 
prevent the elimination of the inde- 
pendent exhibitor. 

2. Launching by the Department of 
Justice of a "sweeping" investigation 
on the West Coast of various alleged tax- 
dodging by industry executives and by 
picture corporations, and of labor re- 
lations between producers and workers. 

3. Point-blank pronouncement by the 
Dept. of Justice that the "code of fair 
practices" so painstakingly contrived by 
distributors to keep the independent ex- 
hibitors quiet for a few more years was 
wholly unsatisfactory in that it sought to 
perpetuate in a slightly different form 
the very "evils" that the Federal Govern- 
ment was bent on eliminating. Not only 
would this "subterfuge" not occasion 
withdrawal of the pending anti-trust 
suits, said the Attorney General for the 
bewhiskered fellow, but it compelled a 
demand for the divorcement of circuit 
theatres from parent producer-distributor 

4. The C. I. 0. and A. F. of L. West 
Coast unions tangled; and although the 


AFL-affiliated I. A. Locals snagged a 
five-year contract from the producers, the 
agreement explicitly excluded a closed 
shop and recognized the validity of exist- 
ing contracts between the producers and 
other labor groups. The C. I. 0., of 
course, yelled "cop" and dragged into 
the situation the N. L. R. B. — which four 
letters are regarded by A. F. of L. units 
as spelling p-o-i-s-o-n. 

5. The I. A. -4 A's brawl anent juris- 
diction over all performers was aired be- 
fore the A. F. of L. Executive Council 
with attendant publicity, mostly on the 
actors' side, that would murder any other 
industry. The fight was "settled" once 
only to be "unsettled" by a quarrel con- 
cerning the immediate future of a hereto- 
fore comparatively inconspicuous minor 
official of the 4-A's upon whose status 
apparently hinges the employment of 
more than 150,000 people and the se- 
curity of billions of dollars worth of 

6. The tenacity with which the bonus 
boys in producer-distributor ranks in 
Hollywood and on Broadway cling to the 
ticker tape announcing the returns from, 
or the avidity with which they burn up 
the roads leading to, various race tracks 

dotting the verdant terrain of these as- 
sumedly United States. 

7. The threat of television to theatre 

Thus the outline of the wholly un- 
tenable position into which the motion 
picture industry has jockeyed itself. No 
branch of the business can honestly claim 
exemption on the basis of not having 
contributed to the mess. We almost for- 
get to include in the list No. 7, relating 
to television, although this is the only 
problem that makes sense. The distribu- 
tor-exhibitor controversy may be cited by 
some as a "tough problem" that has with- 
stood solution by some of the industry's 
"best minds" for many years. The fact 
that this "problem" has attained such 
longevity attests eloquently to the utter 
lack of innate honesty that has charac- 
terized the actions of representatives of 
both groups. 

The labor fusses aforementioned are 
reported upon in detail elsewhere in this 
issue, thus they are skipped over in this 
space. Let's make a hasty appraisal of 
the other "serious problems." 

• Neely Bill a Bust 

First the Neely Bill. It is years since 
the writer messed much with producers, 
distributors, exhibitors or their self- 
appointed (usually) "protectors," but in 
the absence of any visible change in the 
setup he assumes that the same rules of 

Projectionist Day at N. Y. World's Fair, Sept. 7 

EVERYTHING is in readiness for Pro- 
jectionist Day at the New York 
World's Fair on Sept. 7, according to 
P. A. McGuire, of the International Pro- 
jector Corp., who is coordinating the ac- 
tivities of a group of Metropolitan N. Y. 
projection men who are bending every 
effort to make the affair truly representa- 
tive of the craft. 

Scores of Eastern Local Unions have 
already named their representatives for 
the event, as was expected, but the real 
surprise is the gratifying response re- 
ceived from Locals far distant from New 
York. Typical of this response is the ac- 
tion of Miami Local 316 which not only 
"endorses the event 100%" but will be 
represented thereat by several of its 
members. Lou Kaufman, b. a. of Newark 
Local 244 is chairman of the I. A. Locals 

Speeches will be brief, being limited 
to five minutes each. Among those who 
have already accepted invitations to ad- 
dress the gathering are President George 

E. Browne of the I. A.; Mayor Fiorello 
La Guardia of N. Y. City; Nat Golden of 
the U. S. Dept. of Commerce; E. A. 
Williford, president of the S.M.P.E.; 
Earl Hines, president of International 
Projector Corp., and Dr. A. N. Gold- 
smith, consulting engineer and former 
president of the S.M.P.E. Both RCA and 
Altec Service Corp. are tendering their 

Prominent among those in charge of 
arrangements are Harry Rubin, director 
of projection for Paramount Pictures; 
Lester Isaac, director of projection for 
Loew's Theatres, and his associate, M. 
D. O'Brien; Joe Basson, president of 
Local 306; Thad Barrows and Jimmy 
Burke of Local 182, Boston ; Victor Wel- 
man of Cleveland Local 160; Arthur 
Martens and Dick Hayes of Local 650, 
Westchester County, and Frank Cum- 
mings of Long Island Local 640. Further 
information relative to the affair may be 
had from either P. A. McGuire or J. J. 

AUGUST 19 3 9 


the game apply. It required only one 
reading of the Neely measure, however, 
to reach the conclusion that exhibitors are 
chumps if they go for it. 

So, Mr. Independent Exhibitor wants 
block-booking abolished, does he, and the 
practice of individual buying and selling 
substituted therefor? He also wants the 
prospectus of a given picture to reflect 
hairline accuracy? He also wants "lib- 
eral" cancellation privileges for cause? 
Shades of David Harum, but he'll get 

Even a neophyte in the business must 
realize the utter absurdity of merchandis- 
ing film on an individual-picture basis. 
Joe Glutz of Toledo, for example, will 
be so harassed by worry anent a supply 
of product that he'll get down on his 
knees and beg the salesman to "sell me 
just one more." Certainly Joe Glutz will 
enjoy (?) the right to buy; but Mr. Dis- 
tributor still will enjoy the more advan- 
tageous right to sell — and at almost any 
figure he elects. Existing abuses incident 
to block-booking will be as so much 
trivia by comparison with happenings 
under the individual-picture sales plan. 
The mere right of Joe Glutz to buy pic- 
tures will not miraculously expand his 
bankroll to a point where he can outbid 
his circuit theatre competitor, which need 
only bid $2.50 more than Joe on any re- 
lease. Of course, the widely prevalent 
overbuying evil will be eliminated. 

The Neely Bill will provide Mr. Dis- 
tributor with his greatest opportunity 
since the filming of "The Great Train 
Robbery" to get top prices for product. 
It will be a shambles in which innumer- 
able Joe Glutzs will be slaughtered. No- 
where in the reams of comment anent the 
Neely Bill did we find even a passing 
reference to the dangerous precedent set 
by the passage of this measure in de- 
claring open season on legislation against 
the movies, long the target of every re- 
form group and legislative body from 
Augusta to Zanzibar. 

Tax-dodging by ranking producers and 
by major film corporations, together with 
some queer twists in employer-labor re- 
lations, if proven, will constitute a fitting 
companion-piece to that other engaging 
canvas exposed to public view in the 
form of petty-larceny smuggling by some 
top talent names who are earning a paltry 
$2000 weekly. Great stuff, this, for blue- 
noses and legislators. 

The recently promulgated code of fair 
practices designed to clean up existing 
evils in the distributing field was, of 
course, a joke from its inception — apart 
from a worthy cancellation insert. Uncle 
Sam, in rejecting this code, demands the 
outright divestment by producers and 

Don't say "film cement"— Say "FILM-WELD," 
the modern film bind that never thickens, 
spoils or discolors, firmly binds all film, and 
goes twice as far as cement. — adv. 

distributors of all exhibition holdings. 
This governmental ukase occasions one 
of the biggest laughs since the Standard 
Oil Company was dissolved — only to be 
reorganized on a sectional basis that 
made Standard even bigger pumpkins 
than before. 

Somebody should ask the Det. of 
Justice just what is to become of these 
producer affiliated theatres. For example, 
shall we just uproot the Loew houses 
and dump them into the ocean? If not, 
where is there to be found a purchaser 



When other types of rectifying 
devices sicken and lay down, 
Transverter keeps right on de- 
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Ask about its many other ad- 

Consult the nearest office of The 
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Canada, General Theatre Supply 
Co.; or write us 


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Cleveland, Ohio, U. S. A. 

Exclusive Manufacturers 
of the Transverter 

with sufficient capital to lay it on the 
line to the Loew people? Naturally, a 
prospective purchaser could go to the 
banks and float a loan — but this would 
be hedged about with the usual restric- 
tions, and control would probably reside 
for many years to come in the hands of 
those who through financing picture com- 
panies, including Loew, may be said to 
control production. So what? It would be 
just another Standard Oil deal — merely a 
question of right- and left-hand pockets. 

• Bonus Boys at Play 

The passionate devotion of Hollywood 
and Broadway motion picture people to 
racing is so well known as to provide 
the basis for many a mot. Executives, 
players, directors, technicians — the whole 
picture mob — devotes practically three 
months each year to following the bang- 
tails at their favorite California tracks — 
race meetings which deplete the studio 
personnel and occasion wonder that any 
work is done. Leading film executives 
own tracks and horses, and their busi- 
ness pals grace the boards of directors; 
ditto with some leading players. When 
the California tracks are closed, the pic- 
ture mob still manifests considerably 
more interest in the consensus of opinion 
on the fifth at Hialeah, Arlington, Havre 
de Grace and other tracks than they ever 
do about the quality of pictures. Santa 
Anita, the Mecca for the Hollywood mob, 
now being closed, the exhibition field 
may expect a sharp upturn in picture 
quality soon. 

Just a few notes on television. Sales 
of television receivers during the last 
three months in the New York City area 
approximate 300, very few of which were 
bought on the time-payment plan. This 
means that most purchasers are in the 
top-income brackets. The N.B.C. tele pro- 
grams thrice weekly are estimated to have 
an audience of 5000. Five N. Y. City 
theatres have installed tele receivers in 
their lobbies — but it is generally con- 
ceded that tele is a flop as an attention- 
getter. N. B. C. estimates that 1940 will 
see a total Metropolitan N. Y. audience 
for television of 100,000. 

General Electric announced recently 
that means for extending the present 50- 
mile transmiting range of tele images 
were available; but with the chips down 
at an exposition G. E. failed to make 
good on this. 

Bell Telephone Laboratories crowed 
about the successful transmission of tele- 
vision images over a telephone line from 
Madison Square Garden to the N. B. C. 
studios in N. Y. City, a distance of one 
mile. Payoff on this stunt is that such 
transmission is possible for short runs, 
provided that special equalizers are used 
at exchanges and at terminals, plus a 
special amplifier. Experts aver that 



images so transmitted are only 30% as 
good as conventional tele pictures. 

• Home Shows Impress 

The writer sat in on two home demon- 
strations of television, each program of 
approximately IV2 hours duration. Seven 
people viewed the images very comfort- 
ably without straining, and there was 
ample lighting on the screen. Variety 
programs are the most popular; but a 
broadcast of a melodrama proved so en- 
grossing that two spectator-auditors had 
difficulty in restraining their emotions — 
a very significant angle from the stand- 
point of showbusiness. 

Receiver circuits use from 18 to 36 
tubes, in addition to the expensive "eye" 
tube. Current retail prices on the latter 
are : for a 5-inch tube presenting a black- 
and-white image, $27.50; for a green- 
tinted picture, $25; for a 9-inch tube, 
$60; for a 12-inch tube, $75. Life of 
these tubes is estimated to be 1000 hours. 
Their cost is expected to be halved when 
television really gets rolling. 

Attitude of the motion picture industry 
toward television has some interesting 
angles. Picture people refuse flatly to 
cooperate with the tele crowd, reason ad- 
vanced being that it would spur "unfair 
competition" to film theatres. Result is 
that tele people have some difficulty in 
obtaining suitable film program fare, 
bulk of current stuff being independent 
cartoon releases and foreign films. Still, 
it is significant that around the N. B. C. 
tele studios one never hears any expres- 
sion of concern about film supply, the 
assumption being that whenever films are 
needed the tele people will go right out 
and make them. Where this will leave 
the film producers is anybody's guess. 
Incidentally, several film moguls have 
announced a firm determination to keep 
their stars off tele programs; this while 
the radio airwaves currently are clut- 
tered up with the outgivings of dozens of 
America's most prominent players. 

• Baird Theatre Television 

Most recent big noise in television 
circles, from the showbusiness standpoint, 
was the series of big-screen television 
demonstrations given in N. Y. City by 
the Baird Television Co., which has long 
been active in England. Equipment in- 
stalled in a N. Y. studio (which picks 
up images broadcast by N. B. C. and then 
blows them up on a picture sheet) is 
capable of projecting an image 20 by 
15 feet, but studio limitations forced a 
cut to the 9 x 12 foot size. Details of this 
equipment were published in LP. last 
month, p. 21. 

The non-technical boys from the in- 
dustry trade press went into raptures 
about this demonstration, giving out with 
such statements as that the 9 by 12 foot 
images approximated the quality of mo- 


Chief Projectionist, M&P Metropolitan Theatre, 
Boston, Massachusetts 

Projectionists In Important 
Circuit Welcome Altec Men, 
Chief Projectionist Declares 

V^Jur CIRCUIT is pretty well known, I believe, for high operating 
standards, and we are perhaps more than usually anxious to maintain these 
standards. The Altec men help us do this in many ways. 

"I can say that the projectionists in our theatre are always glad to have 
the Altec inspectors come into the projection room. The Altec men work 
in a spirit of friendly cooperation with the projectionists, and I think of 
the Altec men as our own. They take a big load of worry off our projec- 
tionists, and make many helpful suggestions in other matters not imme- 
diately connected with sound. 

"In the matter of sound in our theatre. I think I am safe in saying that 
it is kept at a high quality level at all times, and that the projectionists and 
our Altec inspectors rate real praise for the way they get the fullest pos- 
sible entertainment value from the product shown in our theatre." 


250 West 57th Street • New York City 

AUGUST 19 3 9 




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tion pictures of eight years ago, and 
numerous other effusions. For the benefit 
of I. P. readers it can be said that this 
is the veriest bunk, the Baird tele images, 
while not too inferior considering the 
state of the television art and the fact 
that the images were blown up, being not 
too inferior but approximating rather the 
quality of motion pictures twenty years 
ago. The lighting was decidedly inferior; 
but Baird can blame the N. B. C. studio 
for this; and definition was conspicu- 
ously absent. A start, yes, but nothing to 
write home about. 

Meanwhile reports from England in- 
dicate that the enthusiasm generated 
some months ago by the televising of a 
couple sporting events and the corona- 
tion, which were fed into several theatres 
before overflow crowds, has diminished 
noticeably. "The novelty of television has 
passed," said one prominent British film 
exhibitor recently. Set sales for home use 
have slumped badly in England during 
the past two months, and one hears very 
little these days about the installation of 
tele sets in theatres. 

The writer still can't see television as 
an adjunct to the motion picture theatre, 
whether in England or in the U. S. Tele- 
vision, in order to pay its way (and pay 
it must or be ousted as a potent mer- 
chandising medium), is destined to be 
strictly a home product, much as is radio 
today. Why should anybody pick himself 
up and repair to any communal center 
to see, even on a slightly larger screen, 
the identical program he can see right 
in his own home and without even tak- 
ing off his slippers or putting on a neck- 

tie? The answer is simply that he won't. 

In conclusion, it can be said that if the 
picture business would stop horsing 
around and playing fast and loose with 
its present welfare and future prospects 
(and we mean all branches of the indus- 
try) everybody concerned — and this 
means projectionists on jobs — might 
experience a feeling of security relative 
to the years immediately ahead. Also, 
both the producers and Labor might get 
together and see just how the picture 
business can best meet the challenge of 
home television, instead of standing off 
in the distance and pouting at the tele 
workers the while they calculate the odds 
on the fifth race. This procedure, of 
course, calls for the application of some 
common sense, which may be asking a 
bit too much of the bonus boys. 

Meanwhile Mr. Projectionist has just 
as much at stake and should be as avidly 
interested in the course of the Neely Bill, 
in the outcome of the Government's de- 
mand for the breakup of distributor- 
controlled theatres, and in cheap smug- 
gling and tax-evasion activities by indus- 
try big shots as they are in those hap- 
penings closer at home, such as union 
jurisdictional battles and the like. 


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I.A.-Equity Row Threatens 
Amusement Field Tieup 

PRACTICALLY no person with eyes 
to read need be informed about cur- 
rent happenings affecting the showbusi- 
ness labor situation, as the press wires 
into even the smallest country newspaper 
have been kept hot with releases, very 
palatable because of the motion picture 
angle, anent the I. A.-4 A's battle before 
the A. F. of L. Executive Council. This 
summary therefore need be only a re- 
view of these inter-Labor high jinks. 

The war was on when the 4 A's, fol- 
lowing hearings, suspended the charter 
of its affiliated A. F. A., tossed out its 
leaders — Ralph Whitehead, Sophie 
Tucker and Harry Richman — and chart- 
ered another unit, the A. G. V. A. under 
the temporary leadership of Eddie Cantor, 
to take over the jurisdiction of all show- 
business people except picture workers. 
Miss Tucker and Richman, highly re- 
garded by Equity, were ousted for string- 
ing along with Whitehead, who was 
really the only one the 4 A's were gun- 
ning for. 

What happened thereafter is spread in 
copious measure on the pages of news- 
papers all over the country. President 
George Browne promptly issued an I. A. 
charter to the Tucker-Richman-White- 
head group; and the 4 A's promptly ap- 
pealed to the A. F. of L. Council meet- 
ing in Atlantic City, charging that the 
I. A. action was the "most barefaced 
jurisdictional raid in the history of the 
A. F. of L„" and particularly so in the 
absence of any referendum vote among 
either the A. F. of A. or the I. A. mem- 
berships as to their wishes in the matter. 

• Browne Defends I.A. 

I. A. leader George Browne replied 
significantly that under the I. A. Consti- 
tution he didn't have to consult the I. A. 
Executive Board or its membership be- 
fore issuing the actors' charter; that he 
considered the I. A. charier from the 
A. F. of L. gave his organization juris- 
diction over all workers in the entertain- 
ment field, including actors; that the 
4 A's as late as 1930 had asked the 
A. F. of L. to define their jurisdiction, 
and that when the 4 A's revoked its 
affiliate's charter it in effect left 12,000 
performers "homeless and with no place 
to go" — except possibly into the C. I. 0. 
ranks. This blast exceeded by a wide 
margin previous statements by President 
Browne that he felt the I. A. was entitled 
to film players. 

After a bitter battle of words un- 
paralleled in the history of the A. F. of 
L., the Executive Council acceded to all 
the Equity demands, ruling that the 4 A's 
had permanent jurisdiction over all tal- 
ent and barring the I. A. from any fu- 
ture activity in that field. It was also 
provided that the Tucker-Richman-White- 
head group be reinstated in the A. F. A., 
the charter of which would be restored; 
that a committee be appointed to handle 
A. F. A. affairs for ninety days, after 

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which time an election of officers would 
be held. This decision, a bitter blow to 
I. A. aspirations, apparently settled the 

Equity promptly knocked over this 
proposed settlement, however, despite 
their acceptance of all sections save one 
of the Council's decision, by refusing 
flatly to accept Whitehead under any cir- 
cumstances, althought both Richman and 
Miss Tucker were "more than welcome 
home." The A. F. of L. Council reply 

to the 4-A's reaction was in effect that 
the latter must accept the Council de- 
cision 100% or not at all. Equity de- 
cided that it would be not at all. The 
I. A. let it be known that either White- 
head would be reinstated or the battle 
would continue. President Green made 
frantic efforts to placate the combatants, 
even to the extent of finding a slot for White- 
head in some other labor union; but the 
latter refused to play on this basis. 

The situation as these lines are written 

\ UGUST 19 3 9 


For Peace of Mind 


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For all projectors and sound equipments 

All take-ups wind film on 2, 4 and 5 inch hub reels. 
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New York, N. Y. 

has a number of interesting angles, as fol- 
lows: Equity won't accept Whitehead, there- 
fore the I. A. won't surrender its charter to 
the Whitehead-Tucker-Richman combine ; 
Miss Tucker will be brought up before the 
Equity Council on charges of misconduct, the 
penalty for which will not be less than 
suspension, meaning that she can't work with 
other Equity members; Whitehead, with 
I. A. backing and charter still behind him, 
will continue to organize in the entertain- 
ment field, even while Equity pushes its 
organizing campaign among the same people 
in behalf of its newly-chartered A. G. V. A., 
headed by Cantor; strike talk is heard on 
the part of both Equity and the I. A., with 
each awaiting a move by the other — all of 
which must await the A. F. of L. Conven- 
tion this Fall before another request for 
settlement by the parent body can be made. 

The crucial test will come on Sept. 4 when 
the musical play in which Miss Tucker is 
starred, "Leave It to Me" (h'ya V?), is 
scheduled to reopen in N. Y. after a sum- 
mer suspension. If Miss Tucker is suspended 
by Equity, as appears certain, she will be 
barred from working with other Equity mem- 
bers in this show. Should this occur, it is 
considered certain that the I. A. will retali- 
ate by striking the show. Producer Vinton 
Freedly of the "Leave . . ." show, who has 
already postponed its reopening one week 
to Sept. 4 as a result of the Equity-I. A. 
tangle, announced that he will not reopen 
without Miss Tucker. He might save the 
situation temporarily, of course, by passing 
up the short N. Y. run of the show, but this 
would not solve his problem when "Leave 
. . ." embarks on its projected road tour, 
which Freedly ardently desires to sponsor. 

This probable series of happenings will 
at once draw the first casualties of the fuss 
and signal the opening of a nation-wide 
labor war in the entertainment field. The 
picture producers, through Joseph Schenck, 
let it be known that they sympathized with 
the actors in the dispute. 

Sharply Contrasting Technique 

The tactics employed by both the I. A. 
and Equity during the dispute provides an 
interesting contrast in technique. President 
Browne, for the I. A., issued the actors' 
charter and then sat back with a "So what?" 
attitude to await Equity's move. The latter, 
according to seasoned Labor men, made two 
serious mistakes. First, nobody questioned 
the right of Equity to take such action as 
it deemed necessary relative to the status of 
an affiliate. All Internationals including I. A., 
reserve this right. However, it is pointed 
out that since Equity made no secret that 
it was gunning for only one man, White- 
head, smart procedure would have prompted 
retention of the A. F. A. as an affiliate, the 
while it preferred charges against Whitehead 
as an individual member, to be acted upon 
by the Equity Council. Or Equity could have 
moved in and taken the A. F. A. under its 
wing, while it dealt with Whitehead, which 
action would have automatically rendered 
powerless the Whitehead-Tucker-Richman 
group of officers. Many internationals follow 
this procedure. 

Second, when the A. F. L. Council 
handed down its decision, Equity could have 
accepted the ruling 100%, including White- 
head's reinstatement, because it is conceded 
by all concerned that the general member- 
ship would support Equity in any referendum 
or election vote. Of course, much merit is 
attached to the Equity assertion that White- 
head's reinstatement would place the elec- 
tion machinery in his hands and thus give 
him a great advantage. 

In the final analysis Whitehead is the key 



figure. Thus it is that the status of one man 
is the hinge upon which the whole contro- 
versy turns, a situation which threatens to 
embroil the theatrical field in a controversy 
par excellence, throw 150,000 people out of 
work and endanger the welfare of the entire 
amusement world. 

10% of Production to East, 
Ask N. Y. Labor Groups 

Resolutions passed at 10th District 
(N. Y. State) I. A. Convention included 
one aiming at 100% organization of the 
Schine Circuit and request that at least 
10% of present Coast picture production 
be allotted to N. Y. Latter resolution 
(also approved by N. Y. State Federa- 
tion of Labor) sets forth that 50% of pic- 
tures use N. Y. City as background for 
story, that a large portion of production 
money is advanced by N. Y. banks, that 
the largest distribution market is N. Y. 
City in particular and N. Y. State in gen- 
eral, and that 10% of the total produc- 
tion, if made in N. Y., would employ 
about 10,000 people directly and 40,000 
indirectly. Sol Scoppa of the Lab. work- 
ers sponsored the resolution. 


Westinghouse announces a price reduction 
on the 15-ampere, 60-volt Rectigon bulb 
from $12 to $10. This bulb is used prin- 
cipally in motion picture rectifiers. 


(Continued from page 16) 

universal motor to give a variation in 
the speed of focusing. This focusing 
device should be easily released for manual 


The design shall include a fire shut- 
ter with a device to secure positive 
full opening when the machine is run- 
ning. If of the centrifugal force 
opening type, an indicator should be 
incorporated so that the operator can 
at all times tell that the fire shutter 
is fully opened. This fire shutter 
should not open until the projector 
has reached the speed of 1200 rpm., 
and should close by the time the pro- 
jector has slowed down to that speed. 
This opening and closing speed should 
be adjustable to meet special condi- 
tions where an operating speed of less 
than 1200 rpm. is necessary.* An 
auxiliary control should be included 
so that the light can be flashed with- 
out the necessity of running the ma- 


A positive operating buckle-trip de- 
vice shall be included which will stop 
the mechanism under conditions of 
film breakage, loss of loop, or take- 
up failure. (See "Forward and Back- 
ward Operation of Projector Head".) 

(Auxiliary) : A contact breaker or me- 
chanism to disengage the drive system has 
been suggested as a means of meeting 
the above basic recommendation. 


keeps the box office busy 

Many of your audience may not know a pro- 
jection lens from a sound track, but they do 
know good projection quality and show it in 

Audiences like pictures that are clear and sharp 
from center to edges. They like the brilliance 
and color fidelity of Super-Cinephor Projection. 
You'll enjoy the box office, reaction to Super- 
Cinephors in your projection room. Send for 
details of this truly anastigmatic color-corrected 
projection lens. Bausch & Lomb Optical Co., 
616 St. Paul St., Rochester, N. Y. 



*NOTE:_ The amount of this adjustment to 
meet special conditions shall be determined by 
the intensitv of the light source, degree of 
shutter opening, and speed of operation. 

The noise level of the projector 

head in operation shall be 3 db be- 
low the noise level specification given 
for the whole equipment in that 
part ("Noise Level") of these recom- 
mendations. This recommendation is 
to be met without the use of a booth 
or cumbersome blimp. 

MAGAZINES (Basic) : 

The magazines shall be so designed 
as to be adaptable to reel or spool 
(optional) take-off and take-up and 
shall accommodate up to 1000' reels. 

LENS MOUNT (Basic): 

A sturdy lens mount of sufficient 
size shall be provided to permit the 

use of all specified focal length lenses, 
with a speed of F1.6 (see "Standards 
of Lens Mount Diameters"). Proper 
stability should be provided to elim- 
inate movement and vibration and to 
keep the lens always in its proper 
focal position. Then lens must ac- 
curately rack in and out along its 
horizontal optical axis and not revolve 
while focusing. 

High Speed Head 


(Basic) : 

A high speed projector head shall 
be provided which will operate at a 

AUGUST 19 3 9 


speed of 120 frames per second with 
perfect registration, giving a minimum 
amount of abrasion to the film. The 
high speed projector head shall fulfill 
the recommendations given under 
"Normal-Speed Head," with the excep- 
tion that the noise level specification 
may be disregarded. However, addi- 
tional specifications as given below 
must be met. 

TURES (Basic): 

In the event that by substituting 
the High-Speed Head for Normal-Speed 
Head, the above speed requirement 
cannot be adequately accomplished or 
reconciled with steadiness, it has been 
suggested that separate heads for high 
speed be developed. Special high- 
power motors will be required and 
shall be designed to adequately oper- 
ate the projector at a speed of 120 
frames per second. 


A positive synchronizing shutter sys- 
tem shall be provided to eliminate the 
possibility of shutter slippage. (See 
"Synchronizing". ) 



Considering noise measurements 
made at 45° positions about the pro- 
jector and at a distance of 6' from 
the projector, using a meter which 
employs a 40 db ear loudness weigh- 
ing characteristic and calibrated with 
respect to the standard reference noise 
level of 10 -16 watts per square centi- 
meter, the maximum allowable noise 
level from the whole equipment shall 
be 34 db. 



All screens shall be made with a 
safety-type base — cellulose acetate or 
an equivalent comparable to clear base 
acetate film — this base to be of such 
quality that no discernible color change 
is noticeable over a two-year operation 
period. When a diffusion surface is 
applied to the base, this surface should 
be readily removable so that the 
screen may be easily refinished in 
the event the surface is damaged. 

Don't say "film cement" — Say "FILM-WELD," 
the modern film bind that never thickens, 
spoils or discolors, firmly binds all film, and 
goes twice as far as cement. — adv. 


The screen, over its entire area, 
shall be so designed as to provide: 
(1) optimum transmission (see above 
paragraph) ; (2) optimum diffusion, 
diffraction, or refraction characteris- 
tics; (3) as flat a field as possible; 
and (4) uniform definition. 

The Committee recommends that 
motion picture producing companies, 
manufacturers, and commercial organ- 
izations engaged in process and minia- 
ture work standardize upon the fol- 
lowing screen sizes (specified as use- 
able inside area, exclusive of bind- 
ing) : 

Height Width 

5' x 7' 

8' x 10' 

11' x 14' 

14' x 18' 

Height Width 
16' x 21' 
18' x 24' 

24' x 30' 
27' x 36' 



The following method of measur- 
ing the amount of light falling on a 
screen is recommended : The full 
screen aperture of the projection ma- 
chine is flashed with the shutter open 
and stationary. Nine readings of the 
light intensity are taken at different 
points on the projection side of the 
screen — the four corners, the middle 
of the top and bottom and the two 
sides and the exact center of the 
image. The measurements at the 
corners and edges are made by plac- 
ing the center of the cell in from 
the edge 5% of the total width and 
in from the top and bottom 5% of 
the total height of the projected image. 

The exact height and width of the 
projected image is measured and the 
area of the image computed in square 
feet. The number of square feet of 
the image is multiplied by the aver- 
age of the nine foot-candle readings. 
The result is the number of lumens 
delivered to the screen by the light 
and optical system in question. 

TYPE METER (Basic): 

It is recommended that measure- 
ments of screen brightness be made 
with the Weston Foot-candle meter, 
Model 603, with the cells filtered by 
means of the Weston Viscor filter 

which approximates the color sen- 
sitivity of the human eye. 


It is recommended that all meters 
used in the measurement of screen 
brightness be calibrated at least twice 
a year against known standards. It 
is further recommended that this cali- 
brating be done by an organization 
properly equipped and authorized by 


FS Condensers are ground and 
highly polished to precision accur- 
acy in curvature and focus. They 
will not discolor. 

Available in extra-heat-resisting 
Pyrex Brand glass and also in reg- 
ular glass. 

FS Reflectors are accurately 
made for correct focus, individu- 
ally tested before shipment, and 
protected by a heat-resisting re- 
fractory backing that is non-peel- 
ing. All FS quality optical goods 
are, of course, guaranteed to give 
satisfactory performance. 

Reconditioning Service 

See your dealer about the FS 
service on resilvering and repolish- 
ing reflectors and condensers. 


266 East 43rd Street, New York 


GoldE Triumphs Again I 

National Board of Fire Underwriters AGAIN approves the 


GoldE pioneered the enclosed rewind, designed the first 
and still make the fines': rewind on the market. After 
years of service the GoldE Model -H- Micro Switch 
Rewind operates satisfactorily and without breakdown. 

Absolutely the quietest, safest, most positive in opera- 
tion. Micro Switch controlled. Every projection room 
should be equipped with 


Sold by all reputable Theatre Supply Dealers 

GoldE Mfg. Co. 

1214 W. Madison St. Chicago, Illinois 



the Weston Laboratories to adjust 
and calibrate Weston meters.* 


It has been suggested that the minimum 
intensity of illumination at the screen, 
considering the speed of the lens system 
used, be as follows: The minimum out- 
put of a conventional condenser system 
using an F2.3 system be 12,000 lumens; 
an F2.0 relay type system, 16,000 lumens; 
and an F1.6 relay type system, 25,000 

•NOTE: The Weston meter, Model 603, is rec- 
ognized as standard in Hollywood. Meters which 
do not have proper care and protection from 
rough handling may require calibration oftener 
than twice per year. 


(Continued from page 10) 
example, the Committee is awaiting 
further reports from its members and 
from other committees of the Society 
and from the Academy of M. P. 
Arts & Sciences on the relative merits 
of various modes of processing release 
prints, and as soon as all the material 
is available, the Committee will be 
able to report further on the sub- 

O Handling Release Prints 

The problem of mutilation and mis- 
handling of release prints has received 
very close attention by the Committee. 
Although the 2000-foot reel has received 
complete acceptance by the industry 
and has proved very successful, a num- 
ber of minor problems have arisen dur- 
ing the period of adjustment of the 
industry to the new size. 

The weight of cases, for example, 
has met with objection in some quar- 
ters and seems to have aroused a feel- 
ing that rough handling of the cases 
must be expected and tolerated as 
something inherent in the business. The 
Committee is trying to discourage this 
idea and to show that what is now 
regarded as "ordinary" wear and tear 
should no longer be regarded as or- 
dinary. Contacts have been made with 
the various carriers of film, and good 
cooperation has been shown. It is 
expected, therefore, that some improve- 
ment may soon be evidenced in this 

Recently the question has been re- 
vived as to which is the better way 
of shipping film from the exchanges 
to the theatres — "heads up" or "tails 
up." About two years ago, the Com- 
mittee made an extensive study of the 
subject, principally in the interest of 
determining the best method of splic- 
ing. Drawings and data obtained from 
the film stock manufacturers showed 
that the most satisfactory splice was 

**NOTE: These data have now been made 
available by the Academy, the findings having 
been published in I. P. for May, 1939, p. 20 under 
the heading, "Film Preservative Tests". 

form at theatres equipped with De Luxe Projection. 
Exhibitors everywhere are installing 
Strong Arc Lamps to improve their pro- 
jection and effect the economies possible 
with this modern equipment. 

For Sale by Independent Theatre Supply 
Dealers everywhere. Demonstration in 
your own theatre, without obligation. 

Write today for free catalog on Strong 
unconditionally guaranteed products — 
your guide to better projection. 





Export Offire.- Room 2002, 220 W. 42nd St, New York Ciiy 

flow Many? 

Was this copy dog-eared when it came to you? How 
many men read it ahead of you? 

You would receive a clean, fresh copy ij you had a 
personal subscription — and you wouldn't have to 
wait — you would be first to read it. 

Use coupon below. 

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□ 1 year — 12 issues — $2.00 

□ 2 years — 24 issues — $3.00 
Foreign: Add 50c per year. 

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AUGUST 193 9 

^#Z£&? SAYS- 


fan ueau, -6uti£ttut jkitMJet 
yZaMAimtez evet weaM ou£ you, 
can 'tfet'weif&w i& turn 







These films have been prepared under the supervision of the Projection 
Practice Committee of the Society of Motion Picture Engineers, and are 
designed to be used in theaters, review rooms, exchanges, laboratories, 
factories, and the like for testing the performance of projectors. 

Only complete reels, as described below, are available (no short sections 
or single frequencies). The prices given include shipping charges to all 
points within the United States; shipping charges to other countries are 

35-Mm. Visual Film 

Approximately 500 feet long, consisting of special targets with the aid 
of which travel-ghost, marginal and radial lens aberrations, definition, 
picture jump, and film weave may be detected and corrected. 

Price $37.50 each. 

16-Mm. Sound-Film 

Approximately 400 feet long, consisting of recordings of several speak* 
ing voices, piano, and orchestra; buzz-track; fixed frequencies for focus- 
ing sound optical system; fixed frequencies at constant level, for de- 
termining reproducer characteristics, frequency range, flutter, sound- 
track adjustment, 60- or 96-cycle modulation, etc. 

The recorded frequency range of the voice and music extends to 6000 
cps.; the constant-amplitude frequencies are in 11 steps from 50 cps. to 
6000 cps. 

Price $25.00 each. 

16-Mm. Visual Film 

An optical reduction of the 35-mm. visual test-film, identical as to 
contents and approximately 400 feet long. 
Price $25.00 each. 

Address 1 


Hotel Pennsylvania New York, N. Y. 

made when the film was wound in the 
"head-to-tail" direction, that is, leaving 
the tail out. 

A survey indicated that almost 88 
per cent of the films returned to the 
exchanges had the tails out. This 
meant one of two things, viz., either the 
majority of the theatres of the coun- 
try were not equipped with special 
reels, or they could (or would) not 
spare the additional time required for 
rewinding in order to return the film 
to the exchanges "heads up." 

The representatives of the various 
companies on the Committee felt that 
some expense might be involved if it 
were decided to adopt the "tails up" 
system, which involved an additional 
rewinding at the exchange. Neverthe- 
less, they were willing to go to this 
expense if, as a result, the quality of 
the films delivered to the theatres and 
the resulting projection should prove 
much better. However, in view of the 
overwhelming figures indicating that 
projection in general was definitely on 
a "tails-out-return-to-branch" basis, the 
project was abandoned, and since that 
time it has not been brought before the 
Committee again. 

• Lacquer, Scrap Film 

With regard to the use of lacquer 
in splicing film, investigation showed 
that there was no uniformity of prac- 
tice among the exchanges, some of 
them not using lacquer at all and others 
for first-run films only. The efficacy 
and necessity of using the lacquer are 
now being studied further by the Com- 

The problem of disposing of scrap 
film was also under consideration, and 
a canvass of the companies was made 
to determine what the current prac- 
tices were. It was found that general 
procedure in the exchanges was satis- 
factory and according to regulations, 
although differing somewhat in details. 
This brought up the question also of 
fire regulations in exchanges, and as it 
was reported that the NFPA was en- 
gaged in revising its "Regulations . . .," 
a sub-committee appointed for the pur- 
pose drew up a set of suggestions, re- 
lating to exchanges, for the considera- 
tion of the NFPA. 

Other subjects under consideration by 
the Committee include methods ol 
blooping, dryness and brittleness of 
film, cleaning films in exchanges (sev- 
eral of the companies are now clean- 
ing their films, with gratifying results), 
and handling and storing film cement. 
In addition, the Committee has investi- 
gated a number of new devices, such 
as film cleaners, metal and fiber reel 
bands, new designs of shipping cases 
and reels, etc. 



Plain Talk to Projectionists, 
Dealers and Purchasing Agents 



THREE months ago we introduced 
FILM-WELD, which won immedi- 
ate widespread acceptance because of 
its obvious superiority to ordinary 
film cement. Since then much non- 
sense relative to film splicing in gen- 
eral and film binding agents in par- 
ticular has been circulated — most of 
which emanated from distributors of 
ordinary film cement. 

The campaign against FILM-WELD 
includes the following untruths: (1) 
FILM- WELD advertising contains 
many exaggerated statements (2) "any- 
body" can make a product similar 
to FILM-WELD (3) sponsors of 
FILM- WELD are "fly-by-night" 
people and therefore unreliable. 

Considering these statements in or- 
der, our reply to (1) is to repeat our 



. . . is now being purchased by smart projectionists from these progressive 
dealers (who know a good thing when they see it) : 

Breck Photoplay Supply Co. 
Projection Equip & Maintenance Co. 
B. F. Shearer Co. 

B. F. Shearer Co. 
United Theatre Equipment Co. 

Graham Brothers 

Modern Theatre Equipment Co. 

Capitol City Supply Co. 

Guercio & Barthel Co. 

Ger-Bar, Inc. 

Des Moines Theatre Supply Co. 

Southwest Theatre Equipment Co. 

Louisiana M. P. Equipment Co. 

J. F. Dusman 

Capitol Theatre Supply Co. 
Joe Cifre, Inc. 
Theatre Service & Supply Co. 

a convenient size for every user 

1 oz. bottle 25c 

4 oz. (Special theatre size) 50c 

Vi pi. can 75c 

1 pt. can $1.25 

Amusement Supply Co. 
McArthur Theatre Equipment Co. 

National Equipment Co. 

Quality Theatre Supply Co. 
Scott- Ballantyne Co. 
Western Theatre Supply Co. 

Auburn Theatre Equipment Co. 

Empire Theatre Supply Co. 

United Projector & Film Co. 

Capitol M. P. Supply Co. 
Crown M. P. Supply Co. 

Bryant Theatre Supply Co. 

Akron Theatre Supply Co. 

American Theatre Equipment Co. 
Oliver Theatre Supply Co. 

Standard Theatre Supply Co. 

B. F. Shearer Co. 

Easton Sporting Goods Cc. 

Monarch Theatre Supply Co. 

Hardin Theatre Supply Co'. 

Southwestern Theatre Equipment Co. 
Inter-Mountain Theatre Supply Co. 
B. F. Shearer Co. 

Theatre Supply & Service Co. 
Smith Theatre Supply Co. 

Charleston Theatre Supply Co. 

And at all branches of the 

Perkins Electric Co., Montreal 
J. M. Rice Co., Winnipeg 

Dominion Sound Equipments, Ltd., Montreal 
and Toronto 

previous claims for FILM-WELD 
as follows: 

• Will not thicken, spoil or discolor. 

• Retains its full strength to the last 
drop — even when left uncovered. lie- 
quires no thinning agent. 

• Firmly binds all film — nitrate, ace- 
late, color stock. 

• Goes twice as far as cement. 

And that's not all. We now assert 
that, in addition, FILM-WELD will 
(a) not only bind acetate (safety) 
film to itself but will also bind ace- 
tate stock to nitrate stock (b) make 
a thinner splice than any cement (c) 
positively not buckle film, and (dj 
effectively dissolve the splice-resistant 
coating laid on film by the pre-re- 
lease protective treatment now used 
by all major distributors! 

(2) "Anybody" can I make a prod- 
uct "similar to"" FILM-WELD, which 
is a unique patented formula. 

(3) The sponsor of FILM-WELD, 
far from being a "fly-by-night" per- 
son, has been a working practical 
projectionist for 30 years as a mem- 
ber of I. A. Local 110; has manu- 
factured fine projection equipment 
(including the famous Strong Change- 
over) for the past 20 years, and has 
done business with thousands of pro- 
jectionists and every supply dealer in 
the industry. 

Competitors of FILM-WELD dare 
not deny that it makes a fine bind; 
they merely mumble that "it hard- 
ens". We challenge anybody any- 
where to produce an ounce of FILM- 
WELD that has even thickened — 
with or without the cover removed! 

Projectionists are weary of sticky 
film cement that hardens, that re- 
quires thinner and makes a bumpy 
patch that not infrequently comes 
apart, particularly on pre-release 
treated prints. That's why they are 
flocking to those progressive dealers 
listed on this page to obtain FILM- 
WELD, the modern binding agent 
that looks and flows like water but 
which binds film instantaneously and 

Buy your FILM-WELD at these 
progressive dealers. Remember — 
FILM-WELD is the only binder 
that is sold on a money -back-ij- 
not-satisfied basis. 


1241 South Wabash Avenue 
Chicago Illinois 






If your present sound equipment is not 
adaptable for Push Pull sound reproduction 



avoids obsolescence by 
anticipating improvements 













25c A COPY • $2 A YEAR 

Used for 
High Fidelity 
Long Life 




Get spare photocells for 
every projector. Order 
from your supply dealer! 


1731 Belmont • Chicago 


Visitron cells are available for every type of sound projec- 
tion equipment. Theatre supply dealers can advise the 
correct cell for your equipment. Buy from your supply 
dealer. If you wish to have your old cells tested without 
charge, write to G-M Laboratories, Inc., for instructions for 
shipping. Information furnished promptly. 

nmm to m mi 

The Strong Mogul High Intensity Automatic Re 
Sector Arc Lamp marks a distinct advance in pro- 
jection arc lamp design and construction. It admits 
no competition, for it is in a class by itself and 
provides many fundamental advantages available 
only in Strong lamps. It is our earnest desire that 
every projectionist and exhibitor arrange with his 
Independent Theatre Supply Dealer to see a demon- 
stration in his own theatre to prove to his own 
satisfaction all that is claimed for the Mogul. 

n\z mum mmi 





Export Office: Room 2002, 220 W. 42nd Street, New York City 




MORE LIGHT is the slogan of the day. From news- 
papers and magazines, the lecture platform and the 
school, the public is being taught the sight saving value 
of plenty of light. 

Put your theater in step with this upward trend in 
light intensity. It has popular appeal. People like to 
enter a theater in which they can see their way to their 
seats. And they can do just that in the many theaters 

Write for a free copy of the booklet, "The 

that are now equipped with high intensity projection. 
Think this over if you still have low intensity pro- 
jection. Those first minutes of blindness result from the 
low level of general illumination necessitated by lack of 
light on the screen. Don't let poor lighting drive your 
patrons to other theaters. Install Simplified High 
Intensity projection and attract that growing body of 
theater-goers who appreciate plenty of light. 

Eternal Triangle in Picture Projection."" 






/ooooDoooaaoooDooouo aoDooanaoQDdo naaO°° 

*"^ a AND MODERN ( 

The ivords "National''' and "Suprex" are trade-marks of National Carbon Company, Inc. 


Unit of Union Carbide |l|ij< and Carbon Corporation 


General Offices: 30 East 42nd Street, New York, N. Y. 



OCT 16 1939 /® CIB ,3332e 


Edited by James J. Finn 

Volume 14 


Number 8 

Index and Monthly Chat 5 

The Ashcraft 'Cyclex' Projec- 
tion System 7 

James J. Ftnn 

Projectionist Day is Observed 
at N. Y. World's Fair 


Fundamentals of Mathematics, 

IV 12 

George Logan 

Picture Layout of Simplex SI 
Equipment 16 

Inclusive Simplex SI Equip- 
ment for 200-800 Seat Range 
Theatres 17 

Flicker in Motion Pictures 
Louis D. Grignon 


S.M.P.E. Convention in N. Y., 
Oct. 16-19 Features Varied 
Papers Program 21 

I.P.C. E-7 Dual Shutter and De- 
flector Unit Available for 
Super and Regular Simplex 
Heads 21 

New Strong Mogul H-I Lamp 
I. A. Happenings 


News Notes 
Technical Hints 
Miscellaneous Items 

Published Monthly by 



Circulation Manager, Ruth Entracht 

Subscription Representatives 

Australia: McGills, 183 Elizabeth St., Melbourne 
New Zealand: Te Aro Book Depot, Ltd., 64 Courtenay Place Wellington 
England and Dominions: Wm. Dawson & Sons, Ltd., Pilgrim St., London, E. C. 4. 

Yearly Subscription : United 
States and possessions, $2 (two 
years, $3) ; Canada and foreign 
countries, $2.50. Single copies, 
25 cents. Changes of address 
should be submitted two weeks 
in advance of publication date to 
insure receipt of current issue. 
Entered as second-class matter 

February 8, 1932, at the Post 
Office at New York, N. Y. under 
the act of March 3, 1879. 
Contents copyrighted 1939 by 
James J. Finn Publishing Corp. 
International Projectionist 
is not responsible for personal 
opinions appearing in signed 
articles in its columns. 

Monthly Chat 

DURING the month ensuing since we 
commented on the many and varied 
new additions to the motion picture pro- 
jection equipment lists we have been 
troubled by the thought that in all this 
pushing, tearing and tugging on the 
part of equipment protagonists to gain 
maximum display space for their prod- 
ucts one or more unworthy appliances 
might sneak under the ropes and gain 
widespread acceptance in the field be- 
fore the brakes could be applied through 
the medium of the printed word. 

This statement is not a left-handed 
way of imputing unworthy motives to 
the sponsors of new equipment; on the 
contrary, they are to be congratulated 
and aided in every possible way. Nor is 
it our intent to indulge in any subtle 
criticism of the new products now being 
offered. Yet we would gladly do without 
several new and worthy units if this 
were the price of ducking a single un- 
worthy one. 

This business of new products should 
be of the utmost concern to all projec- 
tionists, for in the great bulk of theatres 
throughout the world fwe exclude the 
plutocratic circuits which employ super- 
visors) the projectionist is the only per- 
son on the premises who knows with 
any degree of certainty the difference 
between a p. e. cell and an intermittent 
movement. This is precisely the reason 
why I. P. has always considered the 
prompt dissemination of news pertaining 
to, and a searching analysis of, new 
equipment to be its prime function. And 
this is precisely why projectionist read- 
ers of I. P. should avidly scan any and 
all such announcements, even to the 
point of registering instant disapproval 
of any conclusions drawn by I. P. with 
which they disagree. In fact, this latter 
course is ardently to be hoped for by 
any editor worthy of the name. Only 
through a free and full discussion of 
such topics (long the cornerstone of 
I. P. policy) can we hope to advance. 

Progress is inevitable in projection 
no iess than in any other art; but we 
shall not withhold our punches against 
trick devices that hove into view under 
the banner of progress. 

• • • 

The indefatigable Phillips researchers 
in Eindhoven. Holland, make sporadic 
forays in behalf of mercury vapor lamps 
as a projection light source, which sal- 
lies are invariably the signal for those 
technical writers who should know better 
to proclaim the problem solved, to the 
dismay of the cautious Phillips group. 
Ditto for television; although the fickle 
British now scorn a previous love, thea- 
tre television. 

• • • 

Progress note: Exchange managers, 
shown a unique footage indicator that 
pastes right onto the real band, re- 
marked: ''Why should we help out those 
projection birds?" Guess the craft is 
just a pushover for double-reels. 

S I I* I 1 3 HI IE B 1 1 1 9 3 9 



THE proving period for Eastman's new 
negative films has been left far behind. 
With their special emulsion qualities re- 
inforced by typical Kodak dependability, 
Plus-X, Super-XX, and Background-X are 
firmly established as successors to other 
notable Eastman films for the motion pic- 
ture industry. Eastman Kodak Company, 
Rochester, N. Y. (J. E. Brulatour, Inc., Dis- 
tributors, Fort Lee, Chicago, Hollywood.) 



for general studio use for all difficult shots 


for backgrounds and general exterior irorh 






Ashcraft ^Cyclex' Projection System 

UTILIZING a means of arc power 
supply which differs radically from 
any system yet put to practical 
use in the projection field, the C. S. 
Ashcraft Mfg. Corp. is now introducing 
to the field a new lamp and accom- 
panying power unit under the overall 
designation of Cyclex*. This article, in 
the nature of a preliminary report and 
outline of the highlights of this new 
system, undoubtedly will evoke no little 
comment by workers in the field, which 
will serve admirably to supplement a 
more detailed exposition of the equip- 
ment which will appear herein subse- 

What is evidently the solution of a 
vexing projection problem for the 
medium- and small-size theatres is now 
at hand. Heretofore those theatres not 
wishing to go into the higher brackets 
of illumination, with correspondingly 
greater expense, have had to utilize 
low-intensity lamps, which give a yellow 
light. Recent demonstrations by Ash- 
craft reveal the availability of a white 
light source of at least twice the in- 
tensity of low-intensity and at a much 
lower cost. 

* Registered Trade-Mark. 


Briefly stated, the Cyclex system of 
projection offers an arc which oper- 
ates on alternating current and, through 
the use of the aforementioned power 
unit, removes the objections heretofore 
cited against this type of arc. A con- 
densed summary of data anent the Cy- 
clex arc follows: 

1. Power: 55-58 amperes at 19 volts, 
supplied by a special rotary converter, 
or frequency changer, which serves both 

2. Carbons: two Suprex 7 mm. posi- 

3. Output: will supply 12 ft. candles 
of illumination (screen center) on a 
17-foot screen. 

4. Color of light: white. 

5. Cost: Average overall cost (power 

The first publication anywhere of 
a projection development that, 
years in the making, has been 
the topic of endless speculation 
as to its whys and wherefors. 
Here are the facts — first in I. P., 
as is usual with all new motion 
picture technical developments. 

and carbons) of 10c an hour, as com- 
pared with Suprex cost of 24c and a 
low-intensity cost of 18c. 

The Cyclex arc is intended primarily 
for those small- and medium-size 
theatres which are now using low- 
intensity arcs. There can be no ques- 
tion as to the superiority of Cyclex 
light in both quantity and color over 
that of the low-intensity arc. 

• The Problem Faced 

Naturally, projectionist interest is 
focused upon the means employed to 
overcome the obvious shortcomings of 
previous a.c. arcs — and therein lies a 
tale which properly requires a retrac- 
ing of steps to review previous expe- 
riences with a.c. arcs, notably that of 
some six years ago when Suprex was 
first introduced. 

With conventional a.c. arcs using 60- 
cycle current the front carbon is the 
only one in focus with the mirror, or 
reflector, and is alternately positive and 
negative 60 times a second. When the 
carbon is positive, light is projected to 
the screen; but when the carbon is 
negative, very little light is projected. 
It follows, therefore, that the screen is 


alternately bright ,and dim 60 times per 

With the shutter idle, the flicker will 
not be apparent because of the inability 
of the eye to follow such rapid changes 
in light intensity, the result of the 
phenomenon known as "persistence of 

In the case of a d.c. arc, however, the 
carbon in focus with the mirror will be 
positive constantly and the projected 
light will be of constant intensity. Such 
a light will appear no different to the 
eye than that projected by the 60-cycle 
a.c. arc — that is, without the shutter 

• Shutter Action Effect 

We turn now to consideration of the 
effect of shutter action. The shutter, 
having two blades and two openings and 
running at the standard speed of 24 
revolutions per second, will cut off the 
light from the screen twice with each 
revolution. Therefore, the frequency of 
the light projected by a d.c. arc, due to 
shutter action, will be 2 x 24, or 48 
cycles, per second — which frequency, if 
the light be of high intensity, can be 
detected by the human eye. 

This effect may be termed inherent 
flicker, since it is a characteristic of 
the projector and bears no relation to 
the nature of current supplying the arc. 
The degree of visibility of this flicker 
depends upon only two things: the in- 
tensity and the color of the projected 

It has been noted that light projected 
by a 60-cycle a.c. arc has no visible 
flicker, but that light projected at a fre- 
quency of 48 cycles per second (the 
shutter frequency, remember) does pre- 
sent a visible flicker provided the in- 
tensity of the light be high enough. Now, 
it is obvious that the lower the fre- 

quency below 48 cycles the more no- 
ticeable will be the flicker. In other 
words, while projected light interrupted 
60 times per second appears to be un- 
interrupted, and light interrupted 48 
times per second is passable, any in- 
terruption of the light at a rate lower 
than 48 times per second will result in 
objectionable flicker. 

The logical question now presents 
itself: If we project a light that is in- 
terrupted 60 times per second, ana then 
cut into this light with a shutter that 
in and of itself interrupts 48 times a 
second this already interrupted light, 
what is the result? The result of this 
imposition of shutter frequency upon 
current frequency is stroboscopic and 
the difference between the two frequen- 
cies is manifested bv a very objection- 
able flicker. Incidentally, the type of 
shutter used has no bearing on the re- 
sults obtained. 

The only possible solution to this 
problem is to determine a harmonic 
(mulitple) of the frequency of the in- 
herent flicker (48 per second), the use 
of which would not require either elec- 
trical or mechanical interlocking means. 
A 48-cycle current would require inter- 
locking of both the converter and the 
projector drive motor, if flicker is to 
bt eliminated, plus a phase-adjusting 
device so that when the current cycle 
is producing the maximum amount of 
light the shutter opening is permitting 
the maximum amount of light to pass 
through. Such a means is wholly im- 

Ashcraft has found that if a current 
fiequency of 96 cycles be used, inter- 
locking is unnecessary. In other words, 
the first, third, fifth and other odd 
multiples — such as 48, 144, and 204 
cycles — do not lend themselves to the 

Installation of Cyclex 
projection system, 
showing lamp and 
relative size of pow- 
er unit and control 
cabinet to other pro- 
jection elements. 

Cyclex system; but the second, fourth, 
sixth and other even multiples — such as 
96, 192, and 288 cycles — are satisfac- 

Explaining his choice of this fre- 
quency, Mr. Ashcraft states: 

• Genesis of Cyclex 

"Cyclex is based on the co-ordination 
of light impulse frequencies. Standard 
projection practice is at the rate of 24 
pictures per second and the interrup- 
tion of the light at the rated 48 times 
per second. We have discovered a means 
of operating the arc so that at the stand- 
ard rate an equal amount of light is 
passed through each and every shutter 
opening, and a like amount of light is 
intercepted by each shutter blade. This, 
or course, is exactly the case existing 
when a d.c. arc is employed; but we 
accomplish the identical result with a.c. 

"The speed of the shutter is imma- 
terial, in a way, as Cyclex does not de- 
pend on exact speeds. However, where 
projection is at exactly 90 feet per 
minute the arc supply frequency is 
about 96 cycles. 

"The reason for the selection of such 
a frequency is apparent when an an- 
alysis is made of various arc current 
supply frequencies used in conjunction 
with standard shutter practice. Such 
analysis shows two factors present in 
the periodic beat apparent on the 
screen: pulsation frequency and pulsa- 
tion intensity. 

"The pulsation intensity curves do not 
follow the pulsation frequency curves, 
but at two points only do they coincide 
at the zero point, the first at 96 cycles 
the other at 192 cycles. The first was 
chosen due to the greater simplicity of 
frequency conversion. At the point of 
contact with the zero line the curve is 
comparatively flat. This characteristic 
allows a latitude or usable band of fre- 
quencies from around 96 cycles, how- 
ever, we can hold the frequency exact 
if necessary and apply the latitude to a 
change in projector speeds. 

"At 96 cycles one complete cycle of 
light will be projected through each 
shutter opening, as one shutter opening 
passes each 1/96 of a second. There 
will be four complete light cycles each 
shutter revolution and, the blades being 
of equal width to the shutter openings, 
will intercept one cycle of light also. 

"An analysis of the graphs of the 
current frequency at 96 cycles super- 
imposed on the time periods of shutter 
openings and closings discloses that al- 
though only one-half the light is pro- 
jected during the half cycle below the 
zero line, or from the carbon facing 
eway from the reflector, an equal 
amount of light is projected through 
each shutter opening continuously re- 
gardless of any change of phase relation 


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a convenient size for every user 

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SO SENSATIONAL has been the 
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now, only four months after its 
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Projectionists are weary of sticky 
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Chicago Illinois 


between the shutter blades and the cur- 
rent cycle." 

• Cyclex Power Unit 

The Cyclex power unit, warranted by 
Ashcraft to be indestructible, utilizes 
only % h.p. for driving the rotary trans- 
former. This latter unit consists of a 
stator upon which is wound the pri- 
mary connected directly to the commer- 
cial frequency power line. The rotor is 
the secondary, with each 30 revolutions 
of the transformer increasing the fre- 
quency 1 cycle. Ordinarily the speed is 
at the relatively low rate of 1080 revo- 

The current of higher frequency is 
taken from the rotor by brushes operat- 
ing on slip rings. The brush current 
density is only one-half that for which 
the brush was designed, the maximum 
current being only 10 amperes at 90 
volts — thus* the wear is infinitismal. 

Both Cyclex arcs are operated from a 
simple rotary unit, yet current is never 
supplied to both arcs from that unit 
simultaneously. By means of two small 
static transformers, with the secondary 
of each connected to its respective arc, 
and a suitable switching device, one arc 
is heated on commercial frequency (60 
cycles while the other is operating on 
a higher frequency supplied by the ro- 
tary transformer. The arcs may be 
switched from one current to the other 
at will, the change being just as rapid 
as the electrical change-over devices. 
The automatic relay is connected direct 
to the ordinary change-over device, re- 
quiring no extra motions. 

Ample taps are provided on the sec- 
ondaries of the transformers for arc cur- 
rent adjustment. While the present ma- 
chines are of the sleeve-bearing type, 
ball-bearing rotary units are available at 
a slight extra cost. Also, any method 
of electrical or hand change-over device 
is applicable to the cycle relay, includ- 
ing slide rods, ropes or pulley types. 
Y-belt and pulleys are used for power 
transmission. While less than % h.p. is 
transmitted, the apparatus is designed 
foi 2.4 h.p. It is very quiet, easy of 
assembly, and provides means of fre- 
quency adjustment for various projection 
machine speeds, the upper pulley being 
of the variable pitch type. 

# Arc Characteristics 

The Cyclex arc has no characteristics 
in common with other arcs, either a.c. 
or d.c; in fact, the Cyclex arc is op- 
erated in a manner which is directly 
contrary to previous practice. Conven- 
tional a.c. arcs utilize an arc gap of from 
.270 to .350 inch; the Cyclex arc gap . 
is of the order of from .100 to .125 

Cyclex arc regulation is accomplished 
by means of a motor without commuta- 
tor or brushes and which draws no more 

Projectionist Day at N. Y. World's Fair 

York World's Fair was observed on 
Sept. 7 by more than 450 projectionists 
and friends of the craft who assembled 
in the Special Events Building and 
participated in a three-hour program 
which was intended to direct the at- 
tention of the general public to the 
attainments of a group which, though 
inconspicuous, contribute greatly to the 
continuing success of the motion pic- 
ture industry. 

Upon completion of the official pro- 
gram numerous groups banded together 
and toured the Fair grounds through- 
out the day. Undeniably these groups 
made their presence felt, but there were 
no casualties. 

E. A. Williford, SMPE prexy, and Dr. 
A. ]\. Goldsmith, enjoy a laugh 

The event was a signal success meas- 
ured in terms of attendance by repre- 
sentatives of many Local Unions from 
far and near no less than because of 
the spirit displayed by participants in 
the program. But of far greater signi- 
ficance, and attesting to the widespread 
interest evoked by the occasion, was 
the deluge of enthusiastic messages 
which descended on the Program Com- 
mittee from Local Unions which were 
prevented, either by distance or other 
factors, from being directly represented 
at the meeting. At least a half dozen 
such messages were received from each 
state and from Canada. In addition, 
the event received a splendid press — 
all of which cannot fail to add immeas- 
urably to the stature of the projectionist 

Many hands played many parts in 

Plutocratic projection supervisors — and 
one rose: Henry Behr, Wilnier & Vin- 
cent; Jim Finn; Frank Cahill. Warner 
Bros., and Harry Rubin, Paramount 

the manifold details incident to the 
planning and execution of the program, 
but the record should show that the 
success of the affair — nay, the reason 
for its very being — is due to the in- 
dividual efforts of P. A. McGuire, of 
International Projector Corp.. who han- 
dled general arrangements for the affair. 
Others pay lip service to the worth and 
standing of the craft; but "Mac" ap- 
parently is the only one who ever trans- 
lates words into action and thereby con- 
tributes something to craft welfare. 

• On the Speakers' List 

Among the prominent personalities 
who appeared on the program E. A. 
Williford, of the National Carbon Co., 
who spoke as president of the S.M.P.E. ; 
Dr. A. N. Goldsmith, widely known 

Nat Golden, W. Byrne, L. V. 306, and 
Dick Hayes, L. V. 650 

consulting engineer and past-president 
of both the S.M.P.E. and the I.R.E.; 
Nat Golden, chief of the Motion Pic- 

power at full load than it does at no 
load; this motor is also warranted to be 
indestructible. The relay for auto- 
matically feeding the carbons is war- 
ranted to be exact at all frequencies, 
which feature is ascribed to a method 
of combination series and differential 

shunt control. One carbon trim is rated 
to burn 4 ] /2 hours, thus making possi- 
ble a 9-hour show on both lamps. 

Additional detailed information rela- 
tive to the theory, construction and op- 
eration of the Cyclex arc will appear in 
subsequent issues of I. P. 



All save one represent the Simplex Sound Dept.: H. Mayer, RCA; and Messrs. 

C. Thompson, C. Alexander, G. Freidl, director, J. Stephans, E. Shorn, H. 

Harnett, K. Schneider, E. Jones, W. Borberg, C. Soehl, L. Reinhold, L. Thome, 

E. G. Mercier, and E. Pirner 

ture Division of the U. S. Dept. of 
Commerce and himself a member of 
Cleveland Local 160; Joseph Basson, 
piesident of N. Y. City Local 306; 
William Reid, of Atlantic City Local 
310, the first projectionist in America 
and who still is active; F. H. Richard- 
son, and Richard Hayes, of Westchester, 
N. Y., Local 650, who voiced the re- 
gret of I. A. President George E. 
Browne at being unable to be present. 
James J. Finn, editor of I. P., also 

Paul Reis, Nat. Carbon Co.; J. K. 
Elderkin, of Forest; Jimmy Burke, b.a. 
of Boston L. U. 182; Ray Duport, also 
of Forest, and George Freidl, of I. P. C. 

spoke, but, he being just a projection 
mug, nobody would ever suspect it 
through reading the various exhibitor 
papers. March of Time made available 
the reel "The Movies March On" as a 
climax piece. 

Among those also present and spotted 
were Thad Barrows and Jimmy Burke, 
of Boston Local 182; Arthur Martens 
and Dick Hayes, of Westchester, N. Y. 
local 650; a large delegation from 
JN. Y. City Local 306 including Wally 
Byrne, b.a., Joe Campbell and a group 
from Miami, Fla., Local 316, who easily 
copped the prize for distance; a group 
from Georgia; A. J. Payette of Spring- 
field, Mass., Local 186; George Fried] 
and a group of ten of his sound dept. 

workers from International Projector 
Corp.; Walter Green, president of Na- 
tional Theatre Supply, and Bert San- 
ford of Altec Service. 

Also, Paul Ries, National Carbon 
Co.; J. K. Elderkin and Ray Duport, of 
Forest Mfg. Corp.; directors of pro- 
jection: Harry Rubin, Paramount; 
Henry Behr, Wilmer & Vincent, and 
Frank Cahill, Warner Bros., and a dele- 
gation from Long Island, N. Y. Local 

What was said and by whom follows: 


By Dr. A. N. Goldsmith 

Consulting Engineer, New York, N. Y. 

t^ELLOW workers in the motion picture 
-*- field: Your capable Committee on Ar- 
rangements, including its dictatorial Chair- 

Chairman P. A. McGuire Thanks 
All 'Day' Participants 

At the conclusion of the addresses P. A. 
McGuire, of the International Projector 
Corp., Chairman of the Arrangements Com- 
mittee, made a brief announcement, stat- 
ing: "We are not here to see motion pic- 
tures as entertainment for that will be 
found in the elaborate recreation provided 
by the New York World's Fair. But 'The 
Movies March On,' shown through the 
courtesy of March of Time, fits in very 
well historically with the program we ar- 
ranged for Projectionist Day. This occa- 
sion was planned to allow the projectionist 
to make his contribution to the great suc- 
cess of this exposition, but we also hope 
that it will enable the public to more 
fully realize the important part the projec- 
tionist plays in the motion picture indus- 

"I wish to thank all who have helped 
make Projectionist Day a success through 
their active participation, and also express 
my appreciation of the encouragement we 
have received from the large number of 
I. A. Locals who have either sent a rep- 
resentative to be present today, have writ- 
ten to us, or wired, expressing their ap- 
proval of this event." 

man, Mr. McGuire, have told me that I 
should be here today to say something to 
you about the art of the projectionist, past, 
present, and future. However, it took little 
of their arbitrary authority to induce me to 
be here, since I have always felt closely 
akin to your group, have admired your 
work, have appreciated its fundamental im- 
portance, and have had faitli in it- future. 

The position of the projectionist in the 
motion picture field is rather a peculiar 
one. He is taken for granted by practically 
everybody and it is calmly assumed that his 
difficult job will be done — and done well. 
The producer, the distributor, the exhibitor, 
and the audience alike take it for granted 
that the picture and sound will be delivered 
satisfactorily and that "the show will go 
on." In a way, this is a high compliment. 
If a job is usually done so thoroughly and 
well that it becomes almost a routine mat- 
ter and that everybody expects it to be 
satisfactory, it is a tribute to the care and 
consistent effort of the projectionist. 

Yet I think that this attitude fails to 
appreciate the importance of the projec- 
tionist in the motion picture set-up. We 

Joe Basson, cornered, forced to listen 

to Thad Barrows, L. V. 182 prexy, give 

out anent alleged Boston culture 

Henry Behr, J. K. Elderkin, Forest Mfg. 
Co., and A. J. Payette, Sec. of L. V. 186 

hear all about the glamorous stars in Holly- 
wood, but every bit of this glamour has to 
pass through less than a square inch of 
film gate to reach the audience. We are 
impressed by the elaborate stage sets and 
studio equipment on the West Coast, but 
it is the projectionist who delivers the re- 
( Continued on page 26 I 



The Fundamentals of Mathematics 

if fl = H, . 

■. fc = 1J< 

a = 1, . 

••6 = 2 A 

a = 2, . 

:b = -x 

a = 3, . 

: b 2 



/F. Simultaneous Equations. 

It will be a help if the reader digest each article as it appears, 
for the ideas presented in subsequent sections hinge upon an under- 
standing of topics discussed in earlier sections. Further, it is desir- 
able that the issues of this series be cached away after reading, as 
back-reference may be useful before the series is completed. 

IT IS worth while to make a study 
of the methods used in solving simul- 
taneous equations, for in the meth- 
ods to be discussed we must necessarily 
use most of the various fundamental 
operations which have been established 
in the three previous sections of this 
series. In brief, we'll get a good review 
in the handling of equations. Also, they 
often crop up in practical problems of 
mechanics and electricity. As a case in 
point, a simultaneous equation solution 
of a branched circuit is included at the 
end of this article. 

Simultaneous equations are two or 
more independent equations involving 
the same unknowns. Thus, if a and b 
are the unknowns, two simultaneous 
equations involving these unknowns 
could be: 

4a+36 = 6 
2a- 6 = 4 

It is evident that these equations are 
independent, because they express dif- 
ferent relations of the unknowns. But 
suppose we have: 

4a+36 = 6 
8a+66 = 12 

These equations, it is apparent, are 
not independent, for if we multiply 
both sides of the first equation by 2, 
the second equation is obtained. Hence 
the second equation can be reduced to 
identity with the first equation simply 
by dividing both sides of the second 
equation by 2; and therefore the second 
equation is not independent of the first 

If we have but one equation in two 
unknowns, such as: 

4a+36 = 6 

it is possible to find an infinite num- 
ber of values for each of the two un- 
knowns which will make the equation 
true; that is, satisfy it. This can be 
easily shown by arbitrarily setting val- 
ues for one unknown and then com- 
puting the other. If in the equation 
immediately above we assign various 
values to a: 

and so on indefinitely. 

But if we have two simultaneous 
equations involving two unknowns, there 
is possible only one value for each of 
the unknowns. In other words, if we 
have two simultaneous equations involv- 
ing a and b, there is only one value for 
a and only one value for b which will 
satisfy both equations. When that one 
possible value for each of the unknowns 
is found the simultaneous equations are 

To reach the solution operations are 
performed on the equations so that a 
single equation is derived from them 
involving just one unknown. This proc- 
ess is called elimination, quite natur- 
ally, for in this single derived equation 
all but one unknown are eliminated. 
Any one of several means of elimina- 
tion may be used, according to which 
means is most conveniently applied to 
a given problem. The several means of 
elimination may be listed: 

1. By addition or subtraction of simul- 
taneous equations. 

2. By substitution of values. 

3. By equating equal expressions. 

Each of these operations have the 
common goal of making all but one un- 
known disappear, so that a numerical 
value can be found for that one un- 
known. Let us consider the first method 

1. Elimination by addition or sub- 
traction of simultaneous equations. 

Assume that we have the appended 
simultaneous equations Nos. 1 and 2. 

1. 4x+3y = 6 

2. 4x-3.v = 18 

Inspection shows that if we add Nos. 
1 and 2 the resultant equation, No. 3, 
will not have a y term. 

1. 4x+3y = 6 

2. 4x-3.v = 18 


= 24 

Solve for x from No. 3: 

3. 8x = 24 

x = 24 


x — 3 

Thus from addition of our simul- 
taneous equations we eliminate one of 
the unknowns, y, and obtain a value for 
the other unknown, x. Now to find the 
value of y, simply place x = 3 in 
either No. 1 or No. 2. 

1. 4x+3y = 6 
(4)(3)+3y = 6 

12+3y = 6 

3y = 6-12 
3y = -6 

y = -2 
Hence the solution of Nos. 1 and 2 
is x = 3 and y = — 2. To check for 
correctness, place these determined val- 
ues in No. 2: 

2. 4x-3y = 18 

(4)(3)-(3)(-2) = 18 
12+ 6 = 18 

18 = 18 check 

We can take this same problem and 
solve it by subtracting the simultaneous 
equations. Subtract equation No. 2 
from equation No. 1: 

1. 4x+3y = 6 

2. 4x-3y = 18 

6y = -12 

y = -2 

Place y = —2 in equation No. 1: 

1. 4x+3y = 6 

4x+(3)(-2) = 6 

4x-6 = 6 

4x = 12 

x = 3 

It is apparent that to eliminate an 
unknown through addition or subtrac- 
tion of simultaneous equations, the co- 
efficient for that unknown must be nu- 
merically the same in each equation. 
Equation Nos. 1 and 2 comply with this 
requirement as they stand — that is, the 
coefficient of x is numerically 4, and 
the coefficient of y is numerically 3, in 
both equations. 

Discretion as to whether we use addi- 
tion or subtraction depends on the 
signs of the equal coefficients. If in 
two equations the coefficients of an un- 
known are equal and of opposite sign, 
addition will make the unknown dis- 
appear. If in two equations the co- 
efficients of an unknown are equal and 
of the same sign, subtraction will elim- 
inate the unknown. 

We know that we can multiply both 
sides of any equation by any chosen 




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number without changing the equation's 
value, and we also know that we can 
divide both sides of any equation by 
any chosen number without changing 
the equation's value. In such operations 
we of course change the magnitude of 
individual coefficients. 

Thus when we are presented, with 
simultaneous equations which do not 
have equal coefficients for some- un- 
known which we wish to eliminate, , we 
simply multiply or divide one or both 
equations by chosen numbers so that 
equal coefficients for the particular un- 
known are formed in both equations. 
Consider the appended simultaneous 
equations Nos. 1 and 2: 

1. 3x+7y = -23 

2. 2x + v = 3 

We- note that we can cause the co- 
efficient of x to be 6 in both equations 
if we multiply equation No. 1 through- 
out by 2. and No. 2 throughout by 3. 
We can then eliminate by subtraction: 

No. 1X2. 6x+14y = -46 
No. 2X3. 6x + 3v = 9 



y = —5 
Place y = — 5 in equation No. 2: 
2x+y = 3 
2x+ (-5) = 3 
2x-5 = 3 
2x = 3+5 
2x = 8 
x = 1 

Thus x = 4 and y = — 5 is the solu- 
tion. For a ready check, place these 
values in equation No. 1. If these val- 
ues satisfy equation our solution is cor- 

1. 3sc+7y = -23 

(3) (4) + (7) (-5) = -23 

12+ (-35) = -23 

12-35 = -23 

-23 = -23 check 

Appended hereto is another example, 
this one showing how an equation may 
be divided throughout by a number so 
that we can proceed with a solution 
by addition: 

1. 21x+7y = 336 

2. -3x+ y = 6 

Divide No. 1 by 7, and add equation No. 2: 
3x+ y = 48 
-3x+ v = 6 
2y = 54 
y = 27 
Place y — 27 in equation No. 2: 
-3x+ y = 6 
-3x+27 = 6 

-3x = 6-27 
-3x = -21 

To check, place x = 7 and y = 27 
in equasion No. 1: 

21x+7y = 336 

(21) (7) + (7) (27) = 336 

147 + 189 = 336 

336 = 336 check 

2. Elimination by substitution of val- 

In this method we take one of the 
equations and transpose terms until we 
obtain an expression for one of the un- 
knowns. We substitute this expression in 
the other equation. By this substitution 
one of the unknowns is eliminated in 
the other equation. This will be clari- 
fied if we work out an actual example. 
Consider the appended simultaneous 
equations Nos. 1 and 2: 

1. x+2y = 10 

2. 2x+ y = 8 
Solve for x from equation No. 1: 

x = 10 -2y 

Substitute this value of x in equation No. 2 
and simplifv: 

2x+ y = 8 

2(10-2y)+y = 8 

20-4y+ y = 8 

-3y = 8-20 

-3y = -12 
y = 4 

Place y = 4 in equation No. 2: 

2x+y = 8 
2x+4 = 8 

2x = 8-4 

2x = 4 

x = 2 

Tc check, place y 
equation No. 1: 

4 and x = 2 ia 

x+2y = 10 

2 +(2) (4) = 10 

2+8 = 10 

10 = 10 

Appended is the solution of another 
example using the substitution method, 
but this time we have omitted most of 
the interpretative phrasing on the side- 
lines. It will be good practice to fol- 
low through the steps for yourself with- 
out benefit of cues. 


3x-4y = -3 


4x+ y = 15 

3x = -3 + 4v 

X= 3 


4x+ v = 15 



3 ;+- v - 15 

- 12 + 16 -v+ „ „ 

(Hint: multiply throughout by 3 to clear 
the fraction) : 

-12 + 16y+3y = 45 

19 y = 45 + 12 

19y = 57 

y = 3 

2. 4x+y = 15 

4x+3 = 15 

4x = 15-3 

4x = 12 

x = 3 

1. 3x-4y = -3 

(3) (3) -(4) (3) = -3 

9-12 = -3 

— 3 = —3 check 

Hence: x = 3, y = 3 

Let's apply this substitution method to 
a practical problem. A gun was fired, 
and the speed of the sound with the 
wind was 1070 feet per second, and 1030 
feet per second against the wind. Find 
the velocity of sound in still air and 
the velocity of the wind. 

We have two unknowns, which we 
shall call x and y. 

Let x = velocity of sound in still air. 

Let y = velocity of the wind. 

The measured velocity, 1070 feet per 
second, represents the velocity of sound 
in still air plus the velocity of the 
wind: x + y = 1070. 

The measured velocity, 1030 feet per 
second, represents the velocity of sound 
in still air minus the velocity of the 
wind: x — y — 1030. 
Hence our simultaneous equations are: 

1. x+y = 1070 

2. x-y = 1030 

Solving these by the substitution 

x = 1030 +y 

1. x+ y = 1070 
(1030 +y)+ y = 1070 

1030 +2y = 1070 

2y = 1070-1030 
2y = 1040 
y = 20 ft. per sec. 

2. x- y = 1030 
x-20 = 1030 

x = 1030+20 
x = 1050 ft. per sec. 
1. x+ y = 1070 

1050+20 = 1070 

1070 = 1070 check 

3. Elimination by equating equal ex- 

In this method we take one of the 
equations and transpose terms until we 
obtain an expression from one of the 
unknowns. Then we take the other 
equation and transpose terms until we 



obtain an expression for the same un- 
known. We equate these two equivalent 
expressions to each other. By this equat- 
ing an unknown is eliminated. An ac- 
tual example will clarify this procedure. 
Consider the appended simultaneous 
equations Nos. 1 and 2: 

1. 6x-2y = 10 

2. 4x+ y = 16 
.Solve for x from equation No. 1: 

6x-2y = 10 

6x = 10 + 2y 
10 + 2y 

Solve for x from equation No. 2: 
4x+ y = 16 
4x = 16— y 
16 -v 

x = ^r 

Thus we have obtained . two expres- 

10+2v 16-y 

— — -=" and — -— 
6 4 

both of which are equal to x. Hence 
they are equal to each other. 



Cross-multiply to clear fractions and sim- 

4(10+2y) = 6(16-;y) 

40+8y = 96- 6y 

4y+8y = 96-40 

14y = 56 

y = 4 

Place y = 4 in equation No. 2 : 

4x+y = 16 

4B+4 = 16 

4z = 16-4 

4x = 12 

x = 3 

To check, place x = 3 and y = 4 in equa- 
tion No. 1: 

6x-2y = 10 

(6) (3)— (2) (4) = 10 

18- 8 =10 

10 = 10 check 

Hence x = & and y = 4 is the cor- 
rect solution. 

When there are two unknowns, as is 
the case in each <of the examples thus 
far worked out, two equations are 
needed to reach a solution. If there are, 
three unknowns, three independent 
equations are needed; if four unknowns, 
four independent equations are needed, 
and so on. Regardless of how many 
unknowns and equations are involved, 
however, the unknowns are ultimately 
found by using any or all of the meth- 
ods we have just outlined. 

We shall conclude this article by 
working out a practical problem in- 
volving three unknowns, requiring the 


set-up of three simultaneous equations 
and the solution of the same. The steps 
by which this problem is solved will be 
particularly informative since they re- 
quire application of most of the im- 
portant ideas we have established in pre- 
vious articles of this series — signs, fac- 
tors, multiplication, division, addition, 
subtraction — as well as application of 
methods 2 and 3 for simultaneous 

In this problem we have given the 
circuit shown in Fig. 1, with constants 
as indicated. We are to find by solu- 
tion of simultaneous equations the val- 
ues of I ls I 2 , and I 3 , the currents in 
each of the three branches. The cur- 
rents are our three unknowns. (This 
problem could be solved, of course, by 
the possibly more familiar method 
whereby we compute the resistance 
equivalent to R 2 and R 3 in parallel- 
but our purpose here is to illustrate 
solution by simultaneous equations.) 

Certain things are known about this 
circuit which will enable us to set up 
three independent equations. The volt- 
age across a — b is common to each 

E-I.R, = I 2 R 2 
I2R2 = I3R3 

And the total current flowing through 
Rj is equal to the sum of the currents 
flowing in R 2 and R 3 : 

i! = Il + I| 

Collecting equations and substituting 
known constants: 

1. 20- 51, = 10I 2 

2. 10I 2 = 15I 3 

3. I, = I,+I, 

Substitute value for I x from equation 
No. 3 in equation No. 1: 

1. 20-51, = 10I 2 

20-5(I.+Ii) = 101, 

4. 20-5I 2 -5I, = 10I 2 

Solve for I, from equation No. 4. Use 
transposition, factoring, and then sim- 

4. 20-5I 2 - 5I 3 = 10I 2 

-5I2-IOI2 = -20+5l 3 
-15I 2 = -5(4-1.,) 



I 2 = 




Solve for I 2 from equation No. 2: 
2. 10I 2 = 151.3 


I. = 



1,= -^ 


Equate the 

expressions for I 2 and simplify 

4.--I. 31, 


3 2 

2(4-1,) = 3(31,) 

8-21, = 91, 

-21,-91, = -J! 

-Ill, = -8 


13 = rri 


T 8 

TI amps ' 

Substitute value of I 2 from equation No. 7 

in No. 6: 

6 I Hs 

6. I, - ■ 

3 8 
12 = 2 X 7I 

1, = ^ 


8. I 2 = l, 1 , amps. 

Substitute values of 1 2 and I 3 from equation 
Nos. 8 and 7 in No. 3: 

3. I, = I 2 +I, 

I. = l,\ + , s , 

9. Ii = 1,", amps. 

As a check, substitute numerical values of 
Ii and I 2 in equation No. 1: 

1. 20-5Ii = 10I 2 

20-5(1*)= 10(1*) 

20-5(f?) = 10(|f) 
220-100 = 120 

120 = 120 check 

Ii = 1* amps. 
I 2 = ItV amps. 
Is = n amps. 

This solution may appear quite 
lengthy and involved, but that is be- 
cause each step has been set down in 
detail. After one becomes skilled in the 
method many of the intermediate steps 
may be shortened or omitted to attain 
the same result. 




— E=;> 







3J IL 




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1. Engineered as a complete visual-sound projection unit and featuring a new lamp and new base. 

2. Film projection head, showing film path. Semi-automatic lubrication — no pump. Intermit- 
tent and upper drive units operate in a bath of fluid oil. Air deflector and cooling fins in combin- 
ation cool film trap and gate. 3. Sound head is the same as that used in Simplex 4-Star system. 

Inclusive Simplex SI Equipment For 
200-800 Seat Range Theatres 

THE new Simplex SI mechanism has 
been designed, manufactured and 
priced to supply definite demand for 
projection equipment which will provide 
better sound and visual projection for 
moderate size theatres with a seating 
capacity ranging from 200 to 800 seats. 
Although moderately priced, the new SI 
mechanism will give very satisfactory 
results in the special field for which it 
is intended. It will enable the theatre 
owner who has been compelled to use 
old, worn-out and obsolete equipment, to 
purchase standard Simplex equipment at 
a price that compares with the low- 
priced inferior equipment now in use. 

This new SI mechanism has many of the 
latest and most modern improvements, 
such as front- and rear-shutters, semi- 
centralized lubrication, air deflector and 
aperture cooling unit, sprocket strippers 
of the non-wrap-around type, fire shut- 
ter safety trip of advance design, and 
also has many other proven Simplex ad- 

"'Hunting-type" gears in the gear train 
of the SI mechanism have proved very 
efficient over a long period in other 
Simplex equipment. This type of gear 
has an uneven number of teeth, which 
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tinue to mesh as the gear revolves. 
Each tooth in the gear meshes with 
every other tooth on the mating gear in 
the course of several revolutions, and 
this results in an even distribution of 
wear, prevents the development of high 
oi low spots, and is an increased as- 
surance of quiet performance. 

Furthermore, with hunting-type gears 
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tooth when the gears are removed tem- 
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hack in mesh in a certain way. The 
gears are simply slipped onto their 
shafts without any regard as to which 
tooth meshes with another. This, of 
course, materially reduces maintenance 
and repair. 

• Gear Train, Intermittent 

The SI mechanism is entirely gear 
driven, but there has been a simplifica- 
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used than in any gear train which has 
been employed heretofore in a Simplex 
professional mechanism. The shutter 
shaft upper sprocket assembly and in- 
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Certain dimensional changes have been 
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Framing knobs project from either 
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entire upper drive unit and intermittent 
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The lower sprocket idler assembly can 
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• Semi-Automatic Lubrication 

Although lubrication of the mechanism 
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these, being of the self-lubricating type, 
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The automatic fire shutter, an im- 

'So this is what you call a 'ground' 

portant safety factor, operates in the fol- 
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Framing and focusing knobs may be 
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by means of a reflector mounted on a 
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To increase visibility and encourage 
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even before better sound equipment was 
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• Pedestal and Lamphouse 

The pedestal is a vibration-proof base 
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Flicker In Motion Pictures 

CONSTANT efforts have been di- 
rected in the technical branches of 
motion picture production and ex- 
hibition toward the removal of effects 
-which make the mechanical processes in 
pictures obvious to the observers and 
detract thereby from the realism and 
entertainment value. Aside from fea- 
tures such as camera angle, lighting, 
sets, backgrounds, sound, etc., two com- 
pletely mechanical effects in pictures 
can cause serious loss of entertainment 
value. These two are flicker and regis- 

This paper does not propose to dis- 
cuss registration; therefore it is neces- 
sary to differentiate this effect from that 
of flicker. Briefly, registration is an 
irregularity in the position of successive 
picture frames on the film or screen. 
Flicker is an irregularity between suc- 
cessive frames in the total amount of 
reflected light from the screen, other 
than that purposely created, from a 
given scene. 

• Many Sources of Flicker 

Flicker still is an important problem 
in the industry, although the serious 
defects are intermittent in nature. 
Flicker is due not only to the frame 
frequency (24 per second) but also is 
the result of other variations super- 
imposed upon the frame frequency. This 
latter effect can be considered in the 
same light as flutter in sound recording 
and reproducing. This paper will lay 
the greatest stress on these harmful 
superimposed variations. 

Consider now the many sources of 
flicker, and group them as follows for 
later consideration : 

(A) Original Photography: 
(1) Set lighting (2) Negative film 

tj. Soc. Mot. Pict. Eng., XXXIII (Sept. 1939). 



Flicker in motion pictures has been 
receiving attention ever since the be- 
ginning of the art, and most of the 
sources of this defect have been mini- 
mized, if not eliminated, by technical 
accomplishments. The paper consti- 
tutes a qualitative review of the now 
prevalent sources of flicker, presenting 
some new concepts, emphasizing the 
sources of major importance at the 
present time, and reporting on two in- 
vestigations made on the problem. 
Flicker and "registration jump" are 
differentiated, and the latter, which is 
really a separate problem, is not con- 
sidered. Some data are presented to 
indicate the magnitude and character- 
istics of the flicker effect. 

(3) Irregular camera motion, including 
motor system (4) Development. 

(B) Printing: 

(1) Lamp irregularity (2) Positive 
(3) Printer motion (4) Development. 

(C) Projection: 

(1) Arc flicker (2) Intermittent shutter 
(3) Projector mechanics. 

(D) Background Projection: 

(1) All of A (2) All of B (3) All 
of C. 

With so many possible sources of 
flicker it is very easy to understand how 
flicker may easily occur. Also, although 
each of the above might be small in 
absolute value, in instances when two 
or more occur at the proper frequencies 
and phase relationships the effect be- 
comes pronounced. This likewise ac- 
counts for the difficulty in tracing, 
separating, and minimizing the major 

Two analyses and invesigations made 
at the Paramount Studios disclosed four 
important facts: 

First, considerable change in reflected 
light can be tolerated by the observer pro- 

vided this change occurs at random inter- 
vals which are not closely spaced or of 
excessive duration. The moment the light 
change become cyclic, the amount of toler- 
able difference decreases sharply to a sur- 
prisingly small value. 

Second, the rate at which the cyclic 
flicker occurs determines the amount of dis- 
turbance to the observer. No accurate de- 
terminations of this fact have been made. 
However, the rate of maximum disturbance 
appears to be between 6 and 8 cycles per 
second. Fig. 1 shows an approximate curve 
representing the apparent disturbing effect 
versus the rate of flicker. 

Third, the change in transmission for 
perceptible periodic flicker occurring at the 
greatest disturbing rate of 6 to 8 cycles 
is about 3 per cent. The greater the 
change in transmission the greater the 

Fourth, the disturbing effect is related 
to the amount of light. The greater the 
intensity the more obvious the defect. 

We shall now discuss the various 
sources of flicker, some briefly and 
others in more detail. 

(A) Original Photography. — The first 
cause of flicker in this group occurs 
in the set lighting. The intensity 
changes of incandescent lamps are of 
a relatively slow and random nature, 
and cause changes in the average bril- 
liance of the scene and are dependent 
upon the regulation and stability of the 
power supply. Arc lamp flicker is 
more likely to be cyclic and therefore 
of a more serious nature. Arc lamp 
flicker generally resolves into slow 
periodic changes such as line-voltage 
and carbon-rotation effects and very fast 
random fluctuations. The very rapid 
fluctuations cause the most trouble in 
background process work, while the 
slow variations can cause serious trouble 
on split-screen shots. This is acknowl- 
edged and must be solved by the lamp 
and carbon manufacturers. 














4 6 8 10 





Snowing the apparent disturbing effect of cyclic flicker as Chart of picture negative in which photographic flicker is 
compared with rate of flicker just perceptible, representing about 3% in transmission 




°/vywv/vwyvV/V/ v/ \/ 




O .5 1.0 1.5 



Chart showing objectionable flicker amounting to about 8 to 

10% variation in transmission 





Flicker due to printing: transmission change 
caused by a ripple voltage of 10 to 15% 

Negative film is known to have ran- 
dom changes in sensitivity, and some 
stocks have cyclic changes occurring at 
at a rate of one cycle in 7 to 12 sec- 
onds, at a speed of 90 feet per minute. 
These variations are not in themselves 
too serious, but should they fall in 
phase with other cyclic changes, then 
the resulting flicker would be noticeable. 
Stocks having cyclic and random sen- 
sitivity have been submitted for use. 
In general these defects have been mini- 

• Irregular Camera Motion 

Irregular camera motion is one of 
the worst offenders at present, but the 
motor system is not blameless and can 
be the cause of flicker. For some time 
the interlock motor system, when used, 
was condemned for all this trouble; 
the fact is that the interlock motor 
system was not the source, but its basis 
of operation allowed the trouble to per- 
sist and frequently amplified it. 

It would appear that, to obtain a 
steady exposure, the speed of the rotat- 
ing shutter, which exposes the film, 
should be as smooth and constant as 
the movement of film through a sound 
recorder. A great deal of time and 
money has been spent by sound equip- 
ment manufacturers and users to re- 
duce flutter, and, as previously men- 
tioned, picture flicker is nothing more 
than flutter. However, cameras generally 
use a slipping belt directly coupled to 
the shutter shaft for a film take-up 
mechanism. Belt condition greatly in- 
fluences the steadiness of take-up, and 
■each instant that a sudden change in 
load occurs the motor system reflects 
that change. 

Even with a motor having no re- 
silience, changes in load can cause 
dicker. The camera undoubtedly con- 
tains mechanical inductances and capac- 
ities (which would include the shutter, 
motor rotors, gears, backlash, motor 
air-gap, flux, etc.) that can become 
resonant. Even though these reactances 
-are inherently stable, the system might 

be thrown into oscillation by a sudden 
shock of small magnitude. This is 
evidenced by circumstances that have 
occurred when belt condition, mechani- 
cal looseness, and shutter action have 
all combined to become oscillatory and 
persistent at a rate well within the 
greatest disturbing region of Fig. 1. 

It was while working on a new motor 
system in conjunction with Erpi that a 
full realization of the true nature of 
the difficulty was reached. A few 
clutches have been tried that gave vary- 
ing degrees of improvement but none 
completely solved the problem. Fig. 2 
shows a chart of a section of picture 
negative in which the flicker was just 
perceptible, representing about 3% 
variation in transmission. Fig. 3 shows 
a similar chart having flicker amounting 
to about 8% to 10% variation in trans- 

Those who have never seen the action 
of a camera shutter might observe the 
opening or closing edge of the shutter 
with a stroboscope, which is accurately 
synchronized with the motor, as either 
of these edges pass the aperture. Obvi- 
ously, any variation in the shutter while 
it is fully open will have no deleterious 

Development of negative is suspected 
of causing some variations, but no con- 
clusive data are yet available. It should 
not be deduced, however, that the 
laboratory is entirely faultless. 

(B) Printing. — When the printer 
light is supplied from a generator or 
rectified alternating current, sufficient 
filtering must be used to reduce intensity 
changes to a small value. The ripple 
voltage should be less than 1 per cent. 
It is true that the normal ripple fre- 
quencies are beyond the greatest dis- 
turbing flicker rate, but the existence 
of 120 cycles in conjunction with other 
flicker frequencies produces a creeping 
density pattern in the projected picture. 
Frequencies increasingly higher than 
120 cycles would undoubtedly cause less 
and less trouble. This particular effect 
is greatly dependent upon the amount 
of light and the density of the various 
parts of the scene. It becomes most 
apparent in scenes including dark skies 
such as in night shots made with filters 
in the daytime. Fig. 4 shows the trans- 
mission change caused by a ripple volt- 
age of 10 to 15 per cent. 

Periodic flicker has been traced to 
printer motion on an earlier type of 
machine, but no data exist on machines 
of current manufacture. In the case 
under investigation the flicker was 
caused by the belt splice which created 
created periodic film-speed changes as 
the stock passed the aperture; i.e., as 
the belt splice passed over the pulley 
the effective radius of the pulley was 
changed, causing a corresponding film- 
speed variation. Fig. 5 shows this effect 
under two conditions, that of normal 

Flicker effect in printing, due 
to belt splices 

12 3 4 




operation and with an exaggerated 
splice. Only the amplitude of the varia- 
tions has changed; the rate having re- 
mained fixed. 

Print development, the same as in 
negative development, has been sus- 
pected of some trouble since, of two 
prints from the same negative, one may 
have flicker and the other not. It is 
true that the printer itself may cause 
this trouble but no analysis has been 

(C) Projection. — The whole subject 
of background projection has been well 
covered by the work of the Academy 
Research Council Process Projection 
Equipment Committee 1 under the chair- 
manship of Farciot Edouart, and a great 
number of the conclusions arrived at 
apply to projectors in general. 

The first item of particular impor- 
tance in projection is steadiness of the 
arc lamp. This factor has been appre- 
ciated for some time and efforts have 
been directed toward its reduction. The 
work done by the aforementioned Com- 
mittee has further advanced arc lamp 

• Projector Shutter Flicker 

Shutter flicker in projection is still 
an important problem and resolves into 
two separate factors. First, constancy 
of light from frame to frame of a par- 
ticular scene; mechanical accuracy of 
all parts; lack of mechanical reson- 
ances; and a stiff or non-resilient and 
well damped motor-drive will all con- 
tribute to improvement. Shutter varia- 
tions amounting to 7 degrees have been 

Second, the effects of shutter rate 
and the manner of eclipsing the picture 
must b? considered. The minimum rate 
is established by the frame frequency. 
During the period that the shutter is, 
open a still picture is being projected, 
but it is possible to demonstrate a 
reduction in flicker by interrupting this 
still picture for a short interval of time 
by an additional blade. This, of course, 
essentially increases the frame frequency 
but leads further to the possibility of 
other physiological factors. 

The question of two-bladed versus 
four or more bladed shutters of various 
dimensions, and one-sided or two-sided 
wipes, is certainly worthy of investi- 
gation. Undoubtedly the best approach 
to a real solution is by an extensive 
series of studies. These tests should 
be made by projecting a single frame 
or still picture at an intensity equal- 
ling that of the good theatre picture 
and always maintaining the same aver- 
age amount of light on the screen re- 
gardless of shutter design. Further, 

these tests should include various values 
of eclipsing times from zero up, with all 
the darkness occurring in one interval 
and the same total amount of darkness 
broken up into two or more intervals, 
single versus double wipes, and instan- 
taneous versus dissolving wipes. After 
reaching a definite conclusion for the 
most satisfactory combination, various 
periodic rates of irregularity could be 
superimposed upon the shutter action 
to obtain more definite and scientific 
data on this particular flicker effect. 

(D) Background Projection. — Back- 
ground projection suffers from all the 
aforementioned ailments except one, 
with the additional penalty of having 
all defects increased two-fold under 
certain circumstances. The one excep- 
tion is shutter flicker in the background 
projector, and this can be eliminated 
only by careful synchronization and by 
making either the camera shutter or 
projector shutter sufficiently greater 
than the other so that the irregularities 
of the two will not overlap. If the 
synchronism does not remain accurate, 
overlapping causes a disastrous result. 

The author appreciates that all the 
matters discussed in this paper are 
controversial, particularly when so little 
concrete evidence can be presented; but 
certainly enough is on hand to indicate 
that progress along this line of endeavor 
should be stimulated. Much work re- 
mains to be done, and this work must 
be coordinated in such a manner that 
all persons involved in the final result 
on the screen work toward the same 
end. Like so many problems in a 
complex art, it will not do much good 
for one branch to assume that its con- 
tribution is commercially sufficient. 
Taken by itself it might be, but when 
put in combination with other units 
to form the complete system, the final 
result may not be good, due to addi- 
tive effects. 

The purpose of this paper has been 
to call the industry's attention once 
again to this serious problem, to indi- 
cate present major sources of difficulty, 
and to discuss them in a limited man- 
ner; and also to offer whatever assist- 
ance our results may provide to those 
who are qualified and equipped to 
carry out further studies. 

Discussion : 

Mr. Morgan: Why is it that nicker 
has now become such a problem? Have 
we always had nicker and not noticed it, 
or have we been adding small distortions 
to the photographic processes so that they 
now add up to make a noticeable flicker? 
How do you determine what you say is 
appreciable flicker? What is the percent- 
age of flicker when you begin to worry 
about it? 

Mr. Grignon: We, as sound men, are 
interested in picture problems, first, be- 
cause we are interested in improving our 
employer's product; and second the Sound 
Department is generally connected with the 
Camera Department through the necessity 
of interlocking motor drives. For years 
we have blamed the motor system for most 
of the causes of flicker but, as pointed 
out in the paper, we have found that it 
was not the motor system itself, but gen- 
erally the type of operation, which per- 
mitted the flicker to exist and did nothing 
to damp it. 

The motor system was not faultless, but 
we did need a new motor system from 
that standpoint. Flicker has always been 
in pictures to some extent, but I can not 
give you a complete answer to that ques- 
tion. Perhaps one of the reasons we 
notice flicker more easily now is that we 
are using more brilliancy in projection. 
With better pictures on the screen it is 
very definite that there will be an increase 
in intensity of screen flicker and that it 
will be more noticeable. 

In answer to the last question: the 
amount of perceptible flicker was deter- 
mined by having a number of persons 
observe results of pictures taken under 
various conditions, and then obtain the 
average transmission differences of the 
(Continued on page 24) 

1 "Recommendations on Process Projection 
Equipment," Research Council of the Academy 
of Motion Picture Arts & Sciences. /. Soc. 
Mot. Pict. Eng., XXXII (June, 1939), p. 589. 

Film Aging, Wear Tests 

Comparative tests of positive film pro- 
duced in the U. S. S. R. and of DuPont 
positive film were made, using various pro- 
jectors, light sources, and sound reproduc- 
tion systems. The greatest wear was found 
to occur in the first few projections of 
both films. The dimensional change of the 
film per projection was found to decrease as 
the number of projections increased. The 
greatest dimensional changes occurred in 
that part of the film in contact with the pro- 
jector gate. 

In general, the silver density of the film 
had a considerably greater effect upon the 
dimensional change of the Soviet film than 
upon that of the DuPont film, and, in gen- 
eral, the DuPont film was found to have 
less dimensional change upon repeated pro- 
jection than the Soviet film. Tests of the 
resistance of the films to tearing showed 
that this was not a decisive factor in the 
useful life of the films. In ■ a study of the 
plasticity of the two films, it was found that 

the Soviet film soon became horny and 
brittle, while the DuPont film largely re- 
tained its plasticity throughout its useful 

The viscosity of one per cent solutions 
of the DuPont film base in acetone were 
essentially constant throughout the useful 
life of the film, showing that only, slight 
structural modification occurred in this film 
base. Similar tests indicated that consid- 
erable structural change was occurring in 
the Soviet film base. The determining fac- 
tors in the useful life of a film were found 
to be the condition of the film perforations 
and the number of scratches and the amount 
of dirt present in the film. The Soviet film 
showed slight gelatin is retained even when 
the film is subjected^ to prolonged heating, 
and that edge-waxing of prints treated by 
this process is unnecessary for use in the 
ordinary type of projection machine. — 
"Aging and Wear of Motion Picture Films 
in Projection", by L. I. Sazhin and L. R. 
Varshavskaya. Kino Photo Chem. Ind., 
pp. 29-39, No. 5, 1938. 



S.M.P.E. Convention in N. Y., Oct. 16-19 
Lists Varied Papers Program 

York City, national headquarters 
oi the Society of Motion Picture En- 
gineers, will be the scene of the twenty- 
fourth annual convention of the So- 
ciety, to be held Oct. 16 to 19, inclusive. 
The technical progress which the motion 
picture industry has made in the past 
year will be reviewed at the Convention, 
in many outstanding technical papers 
presented by the industries' leading en- 
gineers and executives. 

Local arrangements and reception of 
Society delegates will be in the hands 
of an 18-man committee headed by D. E. 
Hyndman, chairman of the Atlantic 
Coast Section. Hotel and transportation 
arrangements are in charge of J. Frank, 
Jr., and his committee. H. Griffin heads 
the committee on convention projection. 
Mrs. 0. F. Neu will act as hostess to 
the ladies, assisted by her Ladies Re- 
ception Committee. 

One of the principal events of the 
Convention will be the banquet and 
dance, to be held Oct. 18 at the Hotel 
Pennsylvania, when the annual presenta- 
tions of the Progress Medal and Journal 
Award will be made. The Progress 
Medal is awarded annually in recog- 
nition of any invention, research or de- 
velopment which has resulted in a signi- 
ficant advance in motion picture tech- 
nology. The Journal Award is made 
to the author or authors of the most 
outstanding paper originally published 
in the Journal of the Society during the 
preceding calendar year. 

• Special Television Showing 

Arrangements have been completed 
for the delegates to witness a special 
television demonstration at the RCA Ex- 
hibit in the New York World's Fair. 
J. Almonte, director of the exhibit, will 
be in charge of the demonstration, which 
will take place after the usual closing 
hour. Delegates wll also see an exhibit 
of the latest type of RCA Photophone 
motion picture sound reproducing equip- 
ment which is housed in the same 
building. The demonstration will be 
held at 9 p.m. Monday, Oct. 16, the 
opening day of the convention. 

A tentatively scheduled convention 
feature will be an address of welcome 
by New York's famous Mayor, F. H. 
LaGuardia. to be delivered at the in- 
formal get-together luncheon. 

Abstracts of those papers of par- 
ticular interest to projectionists are ap- 
pended hereto: 


R. L. Campbell 
Allen B. DuMont Laboratories 

A television film chain with particular 
reference to amplifier, sweep, and power 
circuits in the film pick-up unit is described. 
Many improvements in television circuits 

have been made possible by recent advances 
in circuits and circuit components in radio 
and allied electronic fields. Application of 
some of ihe newer ideas to motion picture 
film pick-up equipment has resulted in im- 
proved- performance and simplicity of op- 

Circuit arrangements which permit flexi- 
bility in transmission standards are consid- 
ered and their application discussed. Also 
the anticipation of possible future improve- 
ments in picture quality is indicated in 
some circuit capabilities. Simplification of 
controls from the television projectionist's 
standpoint is discussed. 



H. Roger 

Rolab Photo-Service Laboratories 

The motion picture is a product of sci- 
ence. There is ample historical material 
available for those who wish to convince 
themselves of this fact; but a brief review 
is given of the work of Muybridge and 
Marey in order to clarify the cause of 
their inventions. The ensuing discussion cen- 
ters around the question, "Has science main- 
tained its interest in the motion picture 
and has it utilized its advantages to its 
full extent?" 

In this paper the word "science" is taken 
broadly and includes research, dissemina- 
tion of knowledge, and industrial applica- 
tion. Motion picture's application to sci- 
ence is divided into two distinct categories 
and are discussed in detail: 

(1) The motion picture as an aid to sci- 
entific research; 

(2) The motion picture as a medium for 
the dissemination of knowledge. 

The paper concludes with descriptions 
and demonstrations of interesting material 

from the files of the Rolab Photo-Science 
Laboratories. Also an inside view is given 
of production activities of an unusual char- 

J. A. Norling 
Loucks and ISorling 

Some problems involved in the produc- 
tion of satisfactory three-dimensional motion 
pictures have not received much mention in 
the literature dealing with stereoscopy. 
Their practical solution has contributed 
marked improvements to the three-dimen- 
sional picture of today. 

Fundamental Problem of 'Depth' 
The fundamental problem in projecting 
three-dimensional pictures is that of pro- 
viding a "right-eye" picture that will reach 
only the right eye and be prevented from 
reaching the left eye and, and to do the 
same for the "left-eye" picture. To attain 
this result two methods have been em- 
ployed with success, namely: the "anaglyph" 
in which substantially complementary col- 
ors are employed in the viewing devices, 
and polarized light. 

The screen surface upon which three- 
dimensional pictures are projected by po- 
larization methods is of extreme importance. 
The selection of the proper type of screen 
raises real problems but these also have 
been overcome in a practical way. 


S. S. Stevens 
Harvard University 

The amount of distortion produced by 
the ear upon a simple sound-wave has been 
measured by analyzing the electrical out- 
put of the ears of animals and by indirect 
experiments with human ears. The amount 
ot distortion in a sound-wave which the 
human ear is just able to detect has also 
been determined, and it is found that the 
{Continued in col. 1, next page) 

I. P. C. E-7 Dual Shutter 
Available for Super and 

DUE to the success of the Simplex 
E-7 mechanism brought about in 
part by the introduction therein of the 
dual (front- and rear-shutter) assem- 
blies therein, International Projector 
Corp. has decided to make this major 
improvement in projection equipment 
available to users of its earlier models — 
the Super Simplex and Simplex Regular 
rear-shutter mechanisms. 

• Now Ready for the Field 

The assembly for the Super Simplex 
mechanism is now ready for distribu- 
tion, the unit for the Regular rear-shut- 
ter mechanism will be available shortly. 
It will be distributed through National 
Theatre Supply Co. which anticipates a 
brisk demand from theatres having Sim- 
plex mechanisms installed. 

This unit provides not only consider- 
ably more illumination on the screen but 
at the same time very definitely im- 
proves the quality of the picture pres- 
entation brought about by sharpness of 

and Deflector Units Made 
Regular Simplex Heads 

definition, reduction of flicker and an 
illusive something that can best be de- 
scribed as a smoother and pleasanter 
picture from the observer's point of 

• Air Deflector Unit 

Included in the assembly moderniza- 
tion kit also is another improvement 
which International introduced at the 
time the E-7 was placed on the market, 
the E-75 Air Deflector and Aperture 
Cooling Unit, which definitely eliminates 
the possibility of interference with the 
arc lamp operation and prevents the 
fluttering of the arc and drawing of 
gases and carbon dust into the projec- 
tion room. This latter assembly also pro- 
vides for more even distribution of light 
in the projected picture. 

The assembly has been so simplified 
that it may be readily attached to any 
Super Simplex mechanism in very short 
time without removing it from its op- 
erating position. 



threshold of audible distortion is intimately 
related to the amount of distortion occur- 
ring in the ear itself. Hence the transmis- 
sion characteristics of the ear determine 
the tolerances for distortion in sound- 



E. K. Carver, Chairman 

Proposals have been received from the 
ISA Secretariat for International Stand- 
ardization of raw-film cores; 16-mm sound- 
film; projection reels; projection reel 
boxes; 8-mm film dimensions; and defini- 
tion and marking of safety film. 

Most of these proposals differ from the 
SMPE standards only in tolerance. Some 
of the tolerances appear to be unimportant 
and some important. The European practice 
for projection reels differs so widely from 
the American practice that it is deemed 
impossible to come to an international 
agreement. Standardization of 16-mm pro- 
jection reel boxes appears to be outside the 
range of useful standardization. 

35- and 16-mm. Track Dimensions 
The international standard definition of 
safety film has been cleared up in all points 
except the question of nitrogen content. 

The question of sound-track dimensions 
for 35-mm and 16-mm film was clarified, to 
a considerable extent, at the Hollywood 
meeting of the Committee, but no definite 
conclusions have yet been reached. No satis- 
factory standard for 16-mm sound-film 
sprockets has yet been attained. 

The publication of the Academy standard 
2000-ft. release print has been delayed pend- 
ing further questions by the Academy. 


The highly diversified activities required 
for the production of a motion picture find 
their effective culmination in the work of 
the theater projectionist. The unusually con- 
centrated value embodied in the reels of 
film corresponding to a feature picture can 
be brought to the theater audience and 
made the basis for commercial returns only 
through the activities of the projectionist. 
Nevertheless the public is little aware of 
what goes on in the projection room. 

The projectionist is in part compensated 
by the likely stability of his activities. His 
present position in the theater is important. 
Future developments in the motion picture 
field, such as three-dimensional sound, wider 
use of color, and the like, will make his 
work even more important. The possible 
inclusion of television projection in theater 
programs will require his mastery of the 
new field which is sufficiently similar to his 
present activities in its broad outline to 
enable its handling by the theater projec- 



J. R. Prater 

Congress Theatre, Palouse, Wash. 

It is the duty of the projectionist to see 
that all projection equipment is kept in 
condition to give excellent service depend- 
ably and efficiently. It is impossible to ac- 
complish these results by depending upon 
memory alone. The projectionist must es- 
tablish and keep written records of all 
necessary maintenance data. He must fol- 
low a written schedule in making inspec- 
tions and in doing maintenance work. He 

New Strong Mogul H-I Lamp 

THE Strong Mogul high-intensity 
automatic reflector arc lamp, now 
being demonstrated by independent 
theatre supply dealers marks a distinct 
advance in projection arc lamp design 
and construction. It has been designed 
to project a volume of light even be- 
yond the normal requirements of 
theatres employing the modern large 
screens of non-reflective surface and 
porous structure, screens that require a 
tremendous increase in light value to 
maintain a satisfactory level of illumina- 

The higher efficiencies attained through 
the use of the Mogul result in this in- 
creased light intensity without a corre- 
sponding increase in operating costs. In 
fact, this improved projection is at- 
tained at a lower cost-per-light unit. 

• Improved Arc Control 

Designed to satisfy fully the most dis- 
criminating exhibitor and projectionist, 
the Mogul high-intensity arc projects a 
steady, brilliant light that is distributed 
uniformly over the complete screen area, 
projecting a picture which fairly 
sparkles and bringing out all the deli- 
cate details and possessing a realistic 
daylight effect. This is the same char- 
acteristic snow-white light used in the 
studios to produce Technicolor prints 
and is so essential to its proper pro- 

Chief among the factors responsible 

for the outstanding performance of the 
Mogul are the ball-bearing motor, an 
arc control system which has separate 
adjustments for the feeding rate of botk 
the positive and negative carbons, 
which are supported by full-floating 
holders and heat-resisting guides near 
their burning end to assure perfect co- 
axial alignment. The accurately formed 
optically corrected elliptical reflector 14 
inches in diameter is held in a cast 
aluminum frame adjustable on its true 
optical axis. 

• Modern Accessories 

The Strong Mogul is pleasingly mod- 
ern in design and of ample size to 
facilitate easy trimming and cleaning 
and to assure proper ventilation with- 
out disturbing the arc, which is sta- 
bilized by an electro-magnetic field. 
There is an ammeter with an illuminated 
dial, trimming and framing light, arc 
imager, inside dowser system inter- 
connected with a mirror flame shield, a 
full-length removable ash tray, and 
three arc vision windows for vertical 
and lateral observation of carbon align- 

Further particulars anent this new 
Mogul lamp are available through either 
independent theatre supply dealers or 
on application by I. P. readers direct 
to the manufacturer, Strong Electric 
Corp., Toledo, Ohio. 

View of the 
new Strong 
Mogul H-I 
lamp shoic- 
ing general 



and lines. 

Note ample 

size for 

h-i work 

must establish a reliable system for check- 
ing and ordering supplies and spare parts 
at regular intervals. 

The projectionist should do as much of 
actual service work as his knowledge, 
ability, tools, and available test equipment 
will permit. At least nine-tenths of trouble 
shooting should be done before any trouble 
exists. He should obtain detailed drawings 
of internal and installation wiring of all 
electrical equipment, besides identifying the 
points at which tests may be made. He 
should prepare a written outline of all tests 

that could be made if various troubles 
existed. Then he should actually make all 
possible tests in advance, wherever possible, 
without causing damage, by deliberately 
creating the trouble and then correcting it. 
He should immediately record the exact re- 
sults of each test in the written outline. In 
this way, simple tests may serve as well as 
or better than elaborate ones. 

The professional service engineer with 
special test equipment is a necessity to the 
finer and more difficult parts of modern 
servicing, but the projectionist who makes 



the best of what resources he has can also 
do a very valuable part of the job. 



J. R. Prater 

Congress Theatre, Palouse, Wash. 

A discussion emphasing the importance of 
actually delivering the benefits of labora- 
tory research and developments to the 
theater patrons who furnish the financial 
support for practically the entire motion 
picture industry. Accomplishments in pho- 
tography, sound recording, projection, and 
sound reproduction are discussed briefly. 
Examples are given of various ways in 
which theatre screen results may suffer re- 
gardless of the excellence of films and 

It is pointed out that whatever can be 
done to increase the projectionist's tech- 
nical knowledge, ability, and pride in good 
workmanship will ultimately benefit the en- 
tire industry. To this end, it is suggested 
that if possible, information from the 
Journal of the S. M. P. E. be made easily 
available to projectionists. 



Fordyce E. Turtle 

Development Dept., Eastman Kodak Co. 

Special slide-changing projectors were de- 
signed and built for the Kodachrome ex- 
hibit in the Eastman building at the New 
York World's Fair. The individual screen 
images are seventeen feet wide and twenty- 
two feet high. Eleven machines are syn- 
chronized so that panoramic scenes one 
hundred and eighty-seven feet long may be 
shown. Indexing of the slides is controlled 
by notches in a sound-film so that the en- 
tire program is automatic. 

The slides in each machine are arranged 
in two rows, and each machine has two 
gates and two complete optical systems. 
All the slides in one row are rigidly bolted 
to a ring-gear forty-eight inches in diameter. 
For each new picture the ring-gear is 
spring-indexed into a new position. While 
one gear is being moved the other is sta- 
tionary, and the picture being projected is 
in the stationary row. An optical com- 
pensator geared to the ring-gear corrects for 
any inaccuracies in indexing, and the image 
is optically "dowelled" on the screen. The 
accuracy of registration is such that one 
slide may be substituted for another with- 
out movement on the screen. 

The light-source used is a 2500-watt, high 
color-temperature tungsten lamp. Water-cells 
and refrigerated air are used to cool the 
film in the gates. The shutter system is 
located between the lamp and the gate in 
order to minimize the heat at the gate. 
Shutters in the two beams are interlocked 
in such a way that while they are being 
moved the light to the screen is constant. 
The cross-dissolve may be rapid or slow 
depending on the type of transition desired. 

Slide projectors similar in structure are 
also being used in the Perisphere Building. 
There the slides are projected in rapid 
enough succession to show motion. 



F. Ehrenhaft and F. G. Back 

The authors have designed a projector 
wherein the optical compensation is effected 
by means of a rotating glass prism. The 

I. A. Happenings 

Chicago Local 110 projectionists have 
been granted a 5% wage increase retro- 
active to Sept. 1, one-half of Union de- 
mand for full restoration of a summer 
cut last year. 

• • • 

The I. A. was returned the victor in a 
N. L. R. B. election held among Holly- 
wood studio workers. Contest resulted in 
4,460 votes for I A. as against 1,967 votes 
in favor of United Studio Technicians 
Guild, a C.I.O.-backed outfit. Latter was 
supported in full-page newspaper ads by 
Screen Writers Guild. The outcomes fore- 
cast an early return by I. A. as a Basic 
Studio Agreement signatory. 

Widespread disciplinary action by the I. A. 
against those who actively supported the 
Technicians Guild was forecast. The latter 
has protested this move to the N.L.R.B. 
as "interference with free choice". Not a 
few I. A. members face expulsion. 

Immediately the results of the balloting 
became known, the I. A. pressed for and 
won a 10% wage increase, retroactive to 
Aug. 12, for the 12,000 studio workers it 
represents. Producers issued statement 
pointing to unyielding strike ultimatum by 
I. A. and added: "It cannot be said that 
the producers granted an increase or that 
they were persuaded that one was fair 
or economically possible; they merely sur- 
rendered. Industry revenues, hard hit by 
the European war, are decreasing to the 
point of disaster. It was purely submission 
to force". 

• • • 

Bested on the West Coast, the C.I.O., 
through its United Theatrical & Motion 

Picture Service Employes Union in New 
York City, made another foray against 
the I. A. In two instances the new union 
has petitioned the State Labor Board for 
bargaining agent rights for ushers, cashiers 
and doormen in two large circuits, in- 
cluding RKO. The larger houses with 
ironclad I. A. contracts are beyond C.I.O. 
reach, of course, but small theatres may 
be susceptible. 

• • • 

Settlement of the I.A.-Equity jurisdic- 
tional conflict centering around the \m- 
erican Federation of Actors, branch of 
Equity, averted a nationwide amusement 
field strike and resulted in a love feasl 
between the combatants, who signatured a 
mutual assistance pact for the future. The 
A. F. A., along with director Ralph White- 
head, whose status precipitated the fire- 
works, passes out of the picture as far 
as the A. F. of L. is concerned, although 
Whitehead says he will continue the or- 

Outcome cemented Equity's hold on aetor 
field, since I. A. promised no further 
moves in this direction. Last-minute settle- 
ment permitted reopening of musical 
"Leave it to Me" and made everybody 
happy— except Whitehead and Harry Rich- 
man, who was given two weeks in which 
to join new actors guild. 

• • • 

Members of seven Seattle, Wash., thea- 
trical unions in negotiating new contracts 
with theatre owners asked the inclusion 
of a "war clause" which would provide- 
for the immediate arbitration of wages 
in the event that war increases living costs 
above normal levels. Also asked for all 
workers is clause anent two weeks" vaca- 
tion with pay. 

problem was originally attacked from the 
viewpoint that by eliminating the errors in- 
herent in the rotating glass prism, a pro- 
jector could be designed that would be 
both simple and practicable. The dimen- 
sions of the rotating glass prism and its 
optical placement result from basic optical 
laws, and the arrangement depends upon 
the size of the image and on the materials. 

Errors inherent in the rotating glass 
prism are (1) Non-linear displacement on 
the screen causing a lack of definition: 
(a) errors of the center rays, (b) errors 
of the corner rays, (c) errors caused by 
shrinking of the film; (2) Chromatical 
errors; (3) Spherical errors: (a) caused 
by the size of the prism, (b) caused by 
the deviation of light in glass; (4) Astig- 
matism caused by the movement of the 
prism; (5) Side images (projection of 
more than one frame on the screen) ; (6) 
Limited focus; (7) Defects by reflection. 

Elimination of these errors was achieved 
by: (1) (a) Limitation of the effective ro- 
tation angle, (b) use of a curved gate, (c) 
establishing the tolerable limits of film 
shrinkage; (2) Calculating size and dis- 
placement of the colors at the extreme 
position of the prism; (3) (a) Use of 
special lenses or additional lenses corrected 
for glass instead of for air, (b) com- 
pensation by a curved gate; (4) Slip-shaped 
diaphragms; (5) Use of diverse dia- 
phragms; (6) Use of special lenses or 
additional lenses; (7) Diaphragms for the 
condenser and screening off the edges of 
the rotating prism. Relation between amount 
of light on the screen, absence of flicker, 
and arrangement of condenser and lamp- 

These factors will be treated by means of 

illustrations and diagrams. A working model 
will be shown and test-films projected to 
illustrate what has been accomplished up 
to now. 



Ben Schlanger 

The various functions of motion picture 
theater auditorium lighting are discussed. 
Particular analysis is made of the lighting 
which is used during the period in which 
the motion picture is projected. Past and 
present lighting practices in this respect 
are explained. The advantages and disad- 
vantages of these practices, and a new type 
of lighting are discussed. It is proposed 
that the illumination levels of the interior 
surface of the auditorium be at greater lev- 
els than have been heretofore found to 
exist. A definite relationship between the 
screen brightness and that of the auditorium 
surfaces is indicated as desirable. 

Recent tendencies toward higher screen 
brightnesses have made a very low intensity 
lighting in the auditorium much more un- 
desirable, and therefore have made it more 
important to arrive at a new solution for 
motion theater auditorium lighting. The 
realism of the projected picture can be con- 
siderably heightened by proper surface 
illumination. Controlled reflected light com- 
ing from the screen and re-reflected from 
the interior surfaces is discussed as a me- 
dium for lighting. 


Patent license agreements have been 
signed by RCA and the Farnsworth Tele- 
vision & Radio Corp. RCA has acquired 



a non-exclusive license under Famsworth 
patents for television receivers, transmitters 
and "other radio and sound recording and 
reproducing apparatus." 

Famsworth has, in turn, acquired a 
standard non-exclusive license for broad- 
cast and television receivers and electrical 
phonographs under RCA patents and also 
other non-exclusive licenses for television 
and broadcast transmitters and "for its 
other field of business." Neither organiza- 
tion acquires any right to grant sub- 
licenses to third parties under the patents 
of the other corporation. 


GoldE Mfg. Co., originators of enclosed 
automatic rewinds, has received the ap- 
proval of the Underwriters Laboratories on 
the re-examination of the Micro-Switch re- 
wind of their manufacture. The Labora- 
tories further recommends, in a recent bul- 
letin, that the Enclosed Rewind be made a 
regular part of all projection room equip- 
ment. This recommendation is taken into 
favorable consideration by insurance under- 

Forest, Expanding, Moves 

Effective Oct. 1, the new address of 
Forest, Inc., is 200 Mount Pleasant Ave., 
Newark, N. J. The change from Belle- 
ville, N. J. to these new and very much 
larger quarters reflects the rapidly ex- 
panding activities of this company, 
which recently added to its line of mag- 
nesium copper sulphide rectifier units a 
new Suprex projection lamp and a 
screen. All products will be marketed 
under the Forest name. 

writers and state code authorities in draft- 
ing their requirements. 

Among the advantages of the GoldE 
rewind are micro-switch operation that as- 
sures positive accurate starting and stop- 
ping — any film breakage stops the rewind 
automatically; automatic stopping when 
door is opened, and all parts carefully and 
expertly finished and assembled. 

Further details are available from either 
your local dealer or GoldE Mfg. Co., 1214 
W. Madison St., Chicago. 


Lincoln Theatres, Inc., and King Coal 
Theatres, Inc., of Marion, Va., has re- 
newed Altec service contracts on six 
theatres, and contracted for service on two 
additional houses. 

M. & P. Theatres, of Boston, Mass., has 
renewed a contract to have Altec service 
the sound in 85 theatres throughout New 


Directors of General Theaters Equipment 
Corp. have declared a cash dividend of 15 
cents per share on the capital stock, pay- 
able Oct. 16 to stockholders of record 
Oct. 6. 


A plan to expand the corporate and 
financial structure of the Radiant Lamp 
Corp., Newark, N. J., has been approved 
by stockholders. The present sales execu- 
tives will continue in direct charge. The 
Radiant plant manufactures a complete 
line of motion picture projection lamps. 


{Continued from page 20) 

samples that were considered as just per- 
ceptibly degraded. 

A discouraging thing about this flicker 
problem is that flicker has not existed 
•day after day and week after week. Flicker 
has been definitely an intermittent prob- 
lem, and during times of serious trouble 
has demanded the attention of many men, 
who, however, to my knowledge have not 
yet arrived at a true and final answer. 
The intermittent nature of this problem 
is undoubtedly due to the many factors 
involved. With all the work that the 
sound engineers have done on flutter it 
seems odd that a situation should exist 
that requires the same quality of motion 
but very little has been done about it, 
and the studios think the manufacturers 
should seriously undertake the problem 
because it is rather costly to have to 
make retakes. 

Lamp Mechanism Vital Factor 
Mr. Joy: This is an interesting paper. 
As manufacturers we have always worked 
along the lines of producing a carbon 
-which will give a steady light. In fact, 
-we have been working along the very same 
lines which Mr. Grignon suggests. As 
evidence of this I refer to Fig. 6, which 
is taken from our paper on "Recent Im- 
provements in Carbons for Motion Pic- 
ture Studio Arc Lighting."* This illus- 
trates that improvement in the carbons 
bas resulted in a very appreciable im- 
provement in light steadiness. It should 
"be realized also that a good lamp me- 
chanism is necessary for the steady burn- 
ing of the carbon. 

In the Technical Bulletin "Recommenda- 
tions on Process Projection Equipment" of 
the Academy Research Council, specifica- 
tions and suggestions are given for burn- 
ing a carbon in a proiection system under 
conditions which, if followed, will go a 
long way toward eliminating any objec- 
tionable flicker. This illustrates again 
that besides having a good carbon it is 
necessary also to burn it properly to obtain 
the steady light desirable for either back- 
ground projection or other lighting appli- 

' To he published in a succeeding issue. 

cations connected with the motion picture 
industry. It is evident that the work of 
Mr. Grignon and also of the Academy 
indicates that we are all striving toward 
the same common end, that is, to make 
a perfect motion picture. 

Mr. Grignon stated in his paper that 
a flicker of around 6 to 8 cycles per 
second in frequency was most noticeable 
to the eye. Was this critical frequency 
established by observation or by some 
theoretical consideration? 

Mr. Grignon: With a large series of. 
tests we finally realized that those irregu- 
larities that were causing us the greatest 
amount of disturbance existed in the re- 
gion of 6 and 8 cycles. This statement is 
not founded on any actual measurement, 
because to make such a measurement 
would require a series of studies and 
other technical data involving a great deal 
of work. However, it was quite apparent 
that this region presented the greatest 
disturbing frequencies. 

Mr. Laube: What is the reaction in 
regard to the way we drive the 20th Cen- 
tury cameras — by drive from the motor 
to the shutter? 

Mr. Grignon : It has been our experi- 
ence that that would probably be better 
than the current type of drive. The best 
way to check this point is with a strobo- 
scope which is accurately synchronized 
with the driving motor, preferably using 
a contractor on the motor to determine 
the flashing periods of the stroboscope. 
Early tests with a non-synchronized strobo- 
scope were found to be misleading. 

Mr. Laube: We feel that we have very 
good motion in the shutters on the 20th 
Century cameras. Stroboscopic tests are 
quite perfect. In background projection 
shots it is very desirable that each frame 
of projected picture remain on the screen 
for a longer time than the total length 
of time the camera_ requires o record ft. 
When I refer to the length of time the 
projected picture remains on the screen, 
I am not including the element of time 
during which the shutter in the projector 
is uncovering or covering the aperture, 
but only the time when the picture has 
its full value on the screen and is not 
being dissolved in or out by the projector 
shutter. If this time period is long enough 
to overlap that of the camera's total re- 

cording time period, I feel that the con- 
dition thus described would be most ideal 
for flicker elimination in background pro- 
jection shots. 

Mr. Grignon: In background projection 
work that is important. If we assume a 
7° variation in shutter operation, which 
we have observed, then, the projection 
shutter should be 14° wider than the 
camera shutter, or vice versa. In using a 
three-head or three-projector type for pro- 
jection there is some improvement be- 
cause the change in any one shutter affects 
only one-third of the total light and the 
result is only one-third as great also, there 
being three shutters, the change is more 
at random and the defect is not as serious. 

Mr. Kellogg: Would you consider a 
disturbance that might occur every four 
seconds as disturbing? 

Mr. Grignon: Offhand I would say that 
such a disturbance, unless of large magni- 
tude or occurring simultaneously with other 
factors, would not be disturbing. 

Studio Practice on Takes 

Mr. Richardson: In the illumination 
of motion pictures, we do not have any 
rotary arc that carries the rotation of 
the positive carbon as high as 15 rpm. 
Practically all the modern lamps of the 
high-intensity rotary type operate at a 
positive rotation speed from 6 to 12 rpm. 

There is another potential cause of 
flicker in the taking of pictures. In some 
studios it has been a practice to stop the 
rotation of the positive carbons during 
picture takes. This has come at the 
insistence of the sound recording depart- 
ments in an attempt to reduce the me- 
chanical noises from the high-intensity spot 
equipment. Some time ago a Committee 
of the Academy made a study of arc 
noise reduction. For this test work we 
had available to the Committee one of 
the quietest stages in the industry, a stage 
on which the ventilation system was made 
inoperative and the ground-noise cut to a 
very low level. The test was made with 
a battery of ten 150-ampere h.-i. arc spots 
centered around a microphone of the type 
used for recording dialog, in a semi-circle 
having a 25-ft. radius. Studies were made 
to ascertain the effects resulting from bring- 
ing the arcs into good trim and then 



cutting the motors off. Our interest was 
primarily in sound. Careful records of 
this test were made, and they are avail- 
able through the Academy to tho